EP0191372B1 - Active agent concentrates for alkaline cleaner having two constituents, method for their fabrication and their use - Google Patents

Description

The invention relates to active ingredient concentrates for alkaline two-component cleaners, processes for their preparation and their use.

To clean rigid materials, for example workpieces made of metal or glass, alkaline cleaning agents are used, which contain caustic soda, orthophosphates, condensed phosphates, silicates, complexing agents, wetting agents and optionally corrosion inhibitors, anti-foaming agents and preservatives. In general, products containing these constituents are marketed as powdery mixtures and are fed discontinuously to the cleaning bath in powder form, the concentration of the cleaning agent in the bath depending on the application and degree of soiling being between 0.1 and 20% by weight.

The prerequisite for the effectiveness of the cleaning solution is compliance with the optimal concentration of the cleaning agent components. This can be determined by titration or a conductivity measurement. The conductivity measurement for determining the concentration can be carried out in conjunction with an automatic metering of the powder mixture in order to set the desired detergent concentration.

A disadvantage of working with powdered products, especially if they contain hygroscopic salts, is that it is difficult to ensure continuous, trouble-free metering. Furthermore, particularly effective nonionic surfactants are sensitive to solid caustic soda. If stored for a long time, they will be oxidized to ether carboxylic acids. This results in a deterioration in the effectiveness of certain cleaning processes and in a spray application of the cleaning solution causes an annoying foam formation.

In addition to powder detergents, the use of liquid alkaline detergent concentrates is also known. According to DE-OS 1467605, the prolonged storage of these concentrates can result in losses of polymer phosphates due to hydrolysis and the poor compatibility of the nonionic wetting and antifoam agents and polymer phosphates contained therein with the remaining detergent concentrate in that the detergents are treated with non-ionic wetting agents and / or anti-foaming agents and water-soluble organic acids or active ingredient concentrate containing complexes which form complexes with the water. These acidic or neutral reacting active ingredient concentrates were then processed into alkaline reacting liquid cleaners by adding an excess of alkali. The disadvantage of such a procedure, however, is that silicate-containing cleaning agents could not be produced in this way, since the surfactants used have high builder concentrations, ie. H. large amounts of silicates in the solution are not compatible.

According to DE-OS 3246080, cleaning concentrates have now been produced from two components, one of which consists essentially of sodium hydroxide solution and the second contains the other cleaning constituents. The latter solution can be adjusted to acidic or neutral pH values, an acidic setting having the advantage that all of its components, in particular the surfactants, are particularly readily soluble. The disclosed two-component cleaners are characterized in particular by the fact that the acidic or neutral component is an aqueous dispersion of silica which has been prepared from pyrogenic or precipitated silica and optionally contains further constituents, such as phosphoric acid, sulfuric acid, polyphosphates, surfactants, stabilizers and / or preservatives can.

A silica obtained from water glass by precipitation with sulfuric acid, washing out and drying was used for the preparation of the silica dispersions. However, the process of precipitating silica by acid treatment of water glass and washing and drying the precipitate is very complex and difficult to carry out, especially on an industrial scale. In addition, the silica obtained in this way is relatively poorly soluble when used in two-component cleaners. Solubility disadvantages arise in particular when the Si0 ₂ / Na ₂ 0 ratio in the cleaning bath is greater than 0.3: 1. Another disadvantage of using precipitated and isolated silica is the fact that, due to the limited solubility of nonionic surfactants, relatively acidic concentrates have to be prepared in order to ensure adequate stabilization. The consequence of this is that large amounts of alkali metal hydroxide have to be added in order to neutralize or to set a preferably alkaline pH of cleaning solutions.

It has now been found that it is in no way necessary to isolate and dry silica precipitated from water glass with the aid of acids. Rather, highly effective liquid two-component cleaner systems with silica dispersions could be obtained, which were obtained in situ by precipitating the silica from sodium or potassium water glass with acids and mixed with stabilizers, surfactants and possibly other builder substances. It is surprising that salts formed during neutralization do not impair the stability of the suspension. In addition, it is possible to produce stable and storable active ingredient concentrates with pH values in the alkaline range (up to pH 11).

The invention therefore relates to active substance concentrates B for alkaline cleaners consisting of two components A and B, one component A of which is a strongly alkaline, predominantly alkali metal hydroxide-containing and used in excess basic aqueous solution and the others re component B is an aqueous dispersion containing silica which, as further additives, comprises anionic, nonionic and / or amphoteric surfactants, builder substances, stabilizers and optionally inorganic mineral acids, complexing agents, preservatives and / or other agents customary in cleaner concentrates, which are characterized in that they contain a silica dispersion which has been adjusted to a pH in the range from 1 to 11 and has been obtained in situ by treating alkali metal silicate solutions with mineral acids or in aqueous solution of its reacting gases.

The invention also relates to a process for the preparation of active ingredient concentrates B for alkaline cleaners consisting of two components A and B, one component A of which is a strongly alkaline aqueous solution which contains predominantly alkali metal hydroxides and is used in excess, and the other component B of which is an aqueous dispersion comprising silica is which contains, as further additives, anionic, nonionic and / or amphoteric surfactants, builders, stabilizers and optionally inorganic mineral acids, complexing agents, preservatives and / or other agents customary in cleaner concentrates, which is characterized in that alkali metal silicate solutions have a pH between 8 and 11 treated with mineral acids or gases reacting acidic in aqueous solution and the silica dispersions thus obtained, without removing the salts formed during the neutralization, with the active ingredient concentrates B necessary components.

The invention also relates to the use of such active substance concentrates B in alkaline two-component cleaners for cleaning rigid materials.

Suitable for the purposes of the invention are aqueous alkali metal silicate solutions whose Si0 ₂ - / M ₂ 0 ratio (M = alkali metal) is in the range from 2 to 3.5. In principle, soda and potash water glass solutions are equally well suited. However, aqueous sodium water glass solutions are preferably used, since these are cheaper and accessible in larger quantities.

In a preferred embodiment of the invention, undiluted technical water glass solutions are used. This has proven to be advantageous simply because a high active substance content is sought for the active substance concentrates that are formed, which, when using dilute solutions, further process steps to increase the active substance content, such as, for B. concentration of the dispersion by evaporation or filtration, required. These steps become unnecessary if concentrated solutions are used.

The silica precipitated in situ is prepared by reacting the water glass solutions mentioned with any mineral acids or gases reacting acidic in aqueous solution, e.g. B. HCI, S0 ₂ and / or C0 ₂ . When using acidic gases, precipitation with CO _{2 is} preferred. When using mineral acids, phosphoric acid and sulfuric acid as well as a mixture of both acids in a weight ratio of 3: 1 to 1: 3 have proven their worth. A ratio of 1: 1 is particularly preferred. In practice, concentrated acids are advantageously used in order to achieve a high active ingredient content in the silica dispersions formed.

During the precipitation reaction, the pH should be between 8 and 10 and the reaction temperature between 60 and 90 ° C. Under these conditions, silica grades are obtained which provide particularly stable dispersions. The specified range of the pH value can advantageously be maintained when working in a buffer system. Alkali metal salts of acids whose anions have a buffering action in the pH range from 8 to 10, for example phosphates, carbonates and / or borates, are particularly suitable as buffers. The buffering salts can be placed in aqueous solution for the precipitation reaction or can form in the course of the precipitation reaction.

When the silica is precipitated from the alkali metal silicate solutions with sulfuric acid, it has proven to be advantageous to present the desired amount of phosphate in the active ingredient concentrate as an aqueous solution and to effect a silica precipitation by simultaneously metering in water glass solution and sulfuric acid.

At the end of the precipitation, the dispersion can be adjusted to the desired pH in the acidic, neutral or alkaline range. With an excess of mineral acid, pH values around 1 can be achieved without this affecting the suitability of the dispersions for alkaline two-component cleaners. However, the dispersions are preferably adjusted alkaline to pH values from 8 to 11, for which purpose aqueous sodium hydroxide solution or potassium hydroxide solution, sodium orthophosphate or potassium orthophosphate, sodium carbonate or potassium carbonate and / or sodium silicates or potassium silicates can be used.

For the intended use of the active compound concentrates according to the invention in alkaline two-component cleaners, a certain content of builder salts which are formed during in-situ precipitation or are added as a buffer is advantageous. Builder salts are understood to mean salts which enhance the cleaning action of the surfactants, for example alkali metal orthophosphates and / or polyphosphates, carbonates, borates and / or sulfates. In particular, alkali metal polyphosphates, i. H. Alkali metal pyrophosphate and / or tripolyphosphate.

In order to achieve a good cleaning effect, it is also expedient to add surfactants to the silica dispersion. Anionic, nonionic and / or amphoteric surfactants are suitable for this purpose. Specifically, there are compounds such as alkylbenzenesulfonates, alkylsulfonates, fatty alcohol sulfates, addition products of ethylene oxide and / or propylene oxide to fatty alcohols, fatty amines and alkylphenols and surface-active ethylene oxide / propylene oxide block polymers. The chain lengths of the alkyl radicals are in the range of 8 to 20 C atoms for the compounds mentioned and in the case of the alkylphenols in the range of 6 to 18 C atoms. Also suitable as amphoteric surfactants are compounds such as alkyldimethylammonium betaines having 12 to 18 carbon atoms in the alkyl radical.

In a preferred embodiment of the present invention, the silicas can be precipitated from alkali metal silicate solutions by mineral acids, even in the presence of the surfactants mentioned. This procedure in particular facilitates the stabilization of alkaline dispersions containing nonionic surfactants.

In addition, the silica dispersions for the active ingredient concentrates according to the invention can also contain complexing agents, such as. B. alkali metal salts of nitrilotriacetic acid, ethylenediaminetetraacetic acid, gluconic acid, citric acid or phosphonic acids (e.g. hydroxyethane-1, 1-diphosphonic acid, aminotrimethylenephosphonic acid and 2-phosphono-1, 2,4-butanetricarboxylic acid).

Compounds are used as stabilizers which prevent the sedimentation of the silica in the dispersions. There are e.g. B. pure substances or mixtures from the group vegetable gum, ie xanthan, and the copolymers of polyalkyl vinyl ethers and carboxylic acid anhydrides, for. B. GANTREZ ^R AN types from GAF Corporation such as copolymers of polymethyl vinyl ethers and maleic anhydride.

The active ingredient concentrate B contains 10 to 26% by weight, preferably 15 to 25% by weight, particularly preferably 18 to 22% by weight, of silica, calculated as SiO ₂ ; 5 to 27% by weight, preferably 8 to 25% by weight, particularly preferably 13 to 24% by weight, builder; 0.5 to 12% by weight, preferably 1 to 10% by weight, particularly preferably 1 to 8% by weight of surfactants; 0.2 to 5% by weight, preferably 0.3 to 3% by weight, particularly preferably 0.5 to 2% by weight, of stabilizers; and 0.5 to 10% by weight, preferably 1 to 8% by weight, particularly preferably 2 to 7% by weight, of complexing agent.

The alkaline component A for the alkaline two-component cleaners consists essentially of sodium hydroxide solution or potassium hydroxide solution. Compounds which are incompatible with the constituents of the silica dispersion component according to the invention, such as, for example, lignin sulfonates, may optionally be considered as further constituents. The aqueous alkali metal hydroxide solution is used in excess for two-component cleaners; this is to be understood as an amount of sodium hydroxide solution or potassium hydroxide solution which is sufficient to give the two-component cleaner concentrate a pH greater than 11, preferably greater than 12, after combining the alkaline and the silica dispersion components according to the invention.

To prepare a two-component cleaning solution, the active ingredient components A and B are mixed in water heated to at least 40 ° C., the silica being converted to water-soluble silicates. PH values greater than 12 are reached.

The advantage of using the active ingredient concentrates B according to the invention which contain silica precipitated in situ is to be seen in the fact that the dispersions are substantially more soluble under the preparation conditions of a detergent bath than dispersions known from the prior art. In addition, the use of silica precipitated in situ offers greater freedom in the formulation of the active ingredient concentrates with regard to the other components. For example, the use of alkaline salts as a builder is made possible. In comparison to systems known from the prior art, a part of the alkali metal alkali can also be saved when the two components for the cleaning bath are combined, if the active compound concentrates according to the invention have already been adjusted to a pH of 8 to 11 and thus neutralization strongly acidic components with large excesses of alkali metal hydroxides is no longer required.

Another advantage of the procedure according to the invention can be seen in the fact that the step of washing out the precipitated silica, which is complex in terms of process engineering, at least for larger amounts of substance, and the steps of separating from the precipitation solution and drying the isolated silica, are superfluous. In addition, it is to be regarded as advantageous that higher salt contents do not impair the stability of the silica dispersions or the effectiveness of the two-component cleaners that arise.

The process is explained in more detail by the examples below.

example 1

To 8 liters of a 2% disodium hydrogenphosphate solution were added at 80 ° C with the help of two metering pumps simultaneously 35 kg of sodium water glass, which was adjusted to a Si0 ₂ / Na ₂ 0 weight ratio of 3.3 and a total solids content of 35%, and 4. 7 kg of a mixture of 98% sulfuric acid and 85% phosphoric acid in a weight ratio of 1: 1 are metered in such that the pH is always kept in the range from 8 to 9. 1.0% xanthan as a stabilizer, 2% of an addition product of 14 EO with nonylphenol and 1% alkylbenzenesulfonic acid were added to the suspension. The dispersion had a pH of 8.5. By adding 5 kg of soda water glass, the pH rose to 10.4. The dispersion remained stable.

Example 2

To 8 liters of a 10% sodium triphosphate solution, 40 kg of potassium water glass with an SiO ₂ / K ₂ 0 weight ratio of 2.1 and a total solids content of 40% and 6 kg of 98% sulfuric acid were simultaneously metered in at 70 ° C., so that a pH Value between 8 and 9 observed has been. 1.5% xanthan as a stabilizer, 2% of an additive of 14 EO to C, 2-18 fatty alcohol and 1% alkylbenzenesulfonic acid were also added to the suspension.

Example 3

60 g of alkylbenzenesulfonic acid and 240 g of nonylphenol + 14 EO were added to 5 liters of a 2% disodium hydrogenphosphate solution in a stirred container and heated to 80.degree. 3.8 kg of a mixture of 98% sulfuric acid and 85% phosphoric acid in a weight ratio of 5: 1 and 40 kg of sodium silicate with an SiO ₂ / Na ₂ O weight ratio of 3.3 and a density of 1 were simultaneously added to this solution. 35g / cm ³ metered in such a way that the pH was kept in the range from 8.8 to 9.2. After the reaction was complete, a dispersion with a pH of 9.1 was formed. 0.3% of a stabilizer mixture of xanthan and a copolymer based on polymethyl vinyl ether / maleic anhydride (GAN-TREZ ^R AN 149) was added to the dispersion.

Example 4

The better dissolution behavior of the silica precipitated in situ compared to commercially available precipitated silica is illustrated by the following example: In a cleaning bath containing 5% sodium hydroxide solution and 1% silica, a complete dissolution of the silica types a) silica precipitated in situ was obtained after 4 minutes at 60 ° C . (stored from Example 1, 3 months) b) Precipitated silica FK 320 after 7 min. DEGUSSA reached.

Example 5

The advantage of silica precipitated in situ with regard to the uniform and stable distribution of surfactants in liquid builder-containing active ingredient concentrates compared to solutions without silica is clear from the comparison of solutions and dispersions: As the active ingredient concentrates a, b, c, d in Table 1 show In the presence of surfactants (here e.g. nonylphenyl + 14 EO), only limited builder concentrations could be selected in order to obtain a solution that was just stable at room temperature. In contrast, in the case of dispersions e and f, surfactants were homogeneously distributable even at high builder concentrations and had a long shelf life.

Active ingredient concentrates:

Example 6

• 20 % Fällungskieselsäure Degussa FK 320
• 5 % Nonylphenol + 14 EO
• 11 % Trinatriumphosphat
• 0,05% Stabilisator

The advantage of silica precipitated in situ compared to conventional, commercially available silica produced by acid precipitation with regard to a uniform and stable distribution of surfactants in liquid builder-containing active ingredient concentrates becomes clear by comparing the dispersion (f) of Example 5 with the dispersion formulated below:

• 20% precipitated silica Degussa FK 320
• 5% nonylphenol + 14 EO
• 11% trisodium phosphate
• 0.05% stabilizer

Rest of water

This dispersion showed measurable segregation after only two months; The wetting agent separated visibly on the surface of the concentrate.

In comparison, the dispersion (f) of Example 5 was still homogeneous even after a long storage period (12 months) and segregation was not observed.

Example 7

Manufacture and use of two-component cleaners

Greased, deep-drawn steel parts stored for three months were degreased in an alkaline cleaner solution (I) prepared with the active ingredient component (B) according to the invention and, in comparison, with a similar alkaline cleaner solution (11) made from powdery cleaner.

The cleaning solutions were composed as follows:

Cleaning solution I:

• 25 g / l silica dispersion (see below) and
• 50 g / l sodium hydroxide solution, 50%

Silica dispersion:

• 20% Si0 ₂
• 10% Na ₃ P0 ₄
• 6% nonylphenol + 14 EO
• 1% stabilizer (xanthan)

Rest of water Cleaning solution 11:

• 50 g / l of a powdered cleaner following

Composition:

• 20% sodium metasilicate
• 5% Na ₃ P0 ₄
• 25% caustic soda
• 47% soda and
• 3% nonylphenol + 14 EO

The cleaning solutions (I) and (11) prepared with the specified components showed a cloud point of 62 ° C. at 80 ° C. at the same active ingredient concentrations (50 g / l). The degreasing time was 12 min with freshly prepared cleaning solution (I) and 13 min with freshly prepared cleaning solution (11).

As Table 2 below shows, the storage of the cleaning solution (I) prepared with the active ingredient concentrate according to the invention had no influence on the degreasing time and cloud point of the cleaning agent. On the other hand, these properties changed with the solution that was produced with the powdered cleaner over a longer storage period. The nonionic surfactants contained therein were broken down into anionic surfactants in the presence of caustic alkalis and atmospheric oxygen. This degradation of the non-ionic surfactants was also associated with an increase in the foaming power, which had a disruptive effect in particular for sprayable cleaning solutions.

Claims (23)

1. Active-substance concentrates B for alkaline cleaning preparations consisting of two components A and B, of which component A is a strongly alkaline, basic aqueous solution predominantly containing alkali metal hydroxides and used in excess while component B is a silica-containing aqueous dispersion which contains as further additives anionic, nonionic and/or amphoteric surfactants, builders, stabilizers and, optionally, inorganic mineral acids, complexing agents, preservatives and/or other additives typically used in concentrated cleaning preparations, characterized in that they contain a silica dispersion adjusted to a pH of from 1 to 11 and obtained in situ by treatment of alkali metal silicate solutions with mineral acids or gases showing an acidic reaction in aqueous solution.

2. Active-substance concentrates as claimed in claim 1, characterized in that they contain a silica dispersion prepared from sodium silicate or potassium silicate solutions.

3. Active-substance concentrates as claimed in claim 2, characterized in that they contain a silica dispersion prepared from sodium silicate or potassium silicate solutions having an SiO₂ to M₂0 (M = Na, K) ratio of from 2 to 3,5.

4. Active-substance concentrates as claimed in claims 1 to 3, characterized in that they contain a silica dispersion precipitated by treatment with sulfuric acid or phosphoric acid or mixtures of sulfuric acid and phosphoric acid in a ratio of 3:1 to 1:3.

5. Active-substance concentrates as claimed in claim 4, characterized in that they contain a silica dispersion precipitated by treatment with a mixture of sulfuric acid and phosphoric acid in a ratio of 1:1.

6. Active-substance concentrates as claimed in claims 1 to 3, characterized in that they contain a silica dispersion precipitated by treatment with HCI, S0₂ and/or C0₂ in aqueous solution.

7. Active-substance concentrates as claimed in claim 6, characterized in that they contain a silica dispersion precipitated by treatment with C0₂ in aqueous solution.

8. Active-substance concentrates as claimed in claims 1 to 7, characterized in that they contain anionic, nonionic and/or amphoteric surfactants.

9. Active-substance concentrates as claimed in claims 1 to 8, characterized in that they are adjusted to a pH value in the range from 8 to 11.

10. Active-substance concentrates as claimed in claims 1 to 9, characterized in that they contain builder salts buffering in the pH range from 8 to 10.

11. Active-substance concentrates as claimed in claim 10, characterized in that they contain alkali metal orthophosphates, alkali metal polyphosphates, alkali metal carbonates, alkali metal borates and/or alkali metal sulfates.

12. A process for the production of active-substance concentrates B for alkaline cleaning preparations consisting of two components A and B, of which component A is a strongly alkaline, basic aqueous solution predominantly containing alkali metal hydroxides and used in excess while component B is a silica-containing aqueous dispersion which contains as further additives anionic, nonionic and/or amphoteric surfactants, builders, stabilizers and, optionally, inorganic mineral acids, complexing agents, preservatives and/or other additives typically used in concentrated cleaning preparations, characterized in that

a) alkali metal silicate solutions are treated with mineral acids or with gases showing an acidic reaction in aqueous solution at a pH value in the range from 8 to 11 and

b) the constituents required for the production of the active-substance concentrates 3 are added to the resulting silica dispersion without removal of the salts formed during the neutralization.

13. A process as claimed in claim 12, characterized in that the silicas are precipitated from the alkali metal solutions in the presence of the surfactants.

14. A process as claimed in claims 12 and 13, characterized in that concentrated waterglass solutions in which the ratio of Si0₂ to M₂0 (M = alkali metal) is from 2 to 3,5 are used as the alkali metal silicate solutions.

15. A process as claimed in claims 12 to 14, characterized in that concentrated mineral acids are used as the mineral acids.

16. A process as claimed in claims 12 to 15, characterized in that sulfuric acid or phosphoric acid or mixtures of sulfuric acid and phosphoric acid in a ratio of 3:1 to 1:3 are used.

17. A process as claimed in claim 16, characterized in that a mixture of sulfuric acid and phosphoric acid in a ratio of 1:1 is used.

18. A process as claimed in claim 17, characterized in that a mixture of 98% sulfuric acid and 85 % phosphoric acid in a ratio by weight of 1:1 is used.

19. A process as claimed in claims 12 to 14, characterized in that hydrogen chloride gas, sulfur dioxide gas and/or carbon dioxide gas is/are used as the gases showing an acidic reaction in aqueous solution.

20. A process as claimed in claim 19, characterized in that carbon dioxide gas is used.

21. A process as claimed in claims 12 to 20, characterized in that the precipitation reaction is carried out in the presence of buffering builders.

22. A process as claimed in claim 21, characterized in that the precipitation reaction is carried out in the presence of alkali metal orthophosphates, alkali metal polyphosphates, alkali metal carbonates, alkali metal borates and/or alkali metal sulfates.

23. The use of the active substance concentrates claimed in claims 1 to 11 in alkaline two- component cleaning preparations for the cleaning of rigid materials, more particularly workpieces of metal or glass.