WO1993020007A1

WO1993020007A1 - Stabilized percarbonate (ii)

Info

Publication number: WO1993020007A1
Application number: PCT/EP1993/000659
Authority: WO
Inventors: Christian Block; Gerald Schreiber; Beatrix Kottwitz
Original assignee: Henkel Kommanditgesellschaft Auf Aktien
Priority date: 1992-03-27
Filing date: 1993-03-18
Publication date: 1993-10-14
Also published as: DE4209924A1

Abstract

In order to make sodium percarbonate sufficiently storage stable to be used in washing agents, it is enveloped with a medium liquid at 25 °C mainly composed of a carboxylic acid or of a carboxylic acid mixture in which the carboxylic acids have at least 8 C atoms, and is then powdered with an organic or inorganic solid material.

Description

"Stabilized Percarbonate (II)"

The present invention relates to stabilized inorganic peroxy compounds, a process for their preparation and their use.

Inorganic peroxy compounds are used today in a wide variety of fields as oxidizing agents. In detergents and cleaning agents, for example, they serve as a bleaching agent for certain stains that are difficult to remove. Sodium perborate in the form of the tetrahydrate is primarily used in these compositions because this compound has an extraordinarily high stability even under unfavorable storage conditions. However, the relatively low content of active oxygen, which is about 10%, is disadvantageous. For these and other reasons, efforts have long been made to find other inorganic peroxy compounds which are suitable for this application. Of particular interest was the so-called sodium percarbonate, an addition compound in which molar Na2C031.5 mol H2O2 are stored in the crystal lattice. In addition to the high content of active oxygen, which is theoretically 15.3% by weight, sodium percarbonate also has a high dissolving rate in water. In its pure form, however, sodium percarbonate is not sufficiently stable in storage so that it is usually only commercially available in a stabilized form. The addition of stabilizing salts, for example alkali metal phosphates and alkali metal silicates, is particularly widespread. However, these commercially available percarbonate grades in many cases do not meet the stability requirements imposed on inorganic per compounds, for example when stored in a humid atmosphere, so that there has been no lack of attempts to achieve greater stabilization in other ways. Numerous proposals of this type are directed to the coating of the percarbonate particles with suitable protective substances, which are intended to ensure that contact with Moisture and other substances impairing stability are reduced. For example, in German Offenlegungsschrift 2203885 fatty acids, fatty acid glycerol esters, fatty acid alkanolamides and long-chain aliphatic alcohols have been proposed as water-insoluble coating substances. In European patent application 30759, long-chain hydrocarbons are used for the same purpose instead of fatty acids and fatty alcohols. Of the coating agents proposed here, the fatty acids are of particular importance for the use of the percarbonate in detergents and cleaning agents, since they are converted into the soaps in the alkaline liquors of these agents and can contribute to the cleaning process. However, the usability of the fatty acids as coating substances is restricted, either because of insufficient stabilization of the percarbonate, because of the stickiness of the granules, which leads to reduced free-flowing properties, or because of the reduced dissolving speed of the coated percarbonate grains in water . For this reason, it is proposed, for example, in US Pat. No. 3,979,318 to incorporate sodium perborate into the hydrophobic substances used as the shell. However, this is a measure that only leads to an improvement in individual cases and also uses the material that is to be substituted.

The proposal of the older, unpublished application DE P 41 09 954.0 leads to better results overall, to use a mixture of low and high melting long-chain aliphatic carboxylic acids for the coating of the percarbonate.

The present invention is also based on the object of finding another possibility for stabilization with the aid of long-chain aliphatic carboxylic acids, which leads to better results overall.

Surprisingly, it was found that, under certain circumstances, a particularly effective stabilization can be achieved with a medium which is liquid at room temperature.

The invention relates to a sodium percarbonate, which by coating with a liquid at 25 ° C, which consists predominantly of a carboxylic acid or a carboxylic acid mixture, the carboxylic acid have at least 8 carbon atoms, and subsequent powdering with an organic or inorganic solid is stabilized against decomposition. Preferably 5 to 10% by weight of the liquid medium and 1 to 10% by weight of the powder substance are applied in the finished product.

The percarbonate stabilized according to the invention is extraordinarily resistant even in a humid and warm atmosphere, is good at free-flowing, does not clump and dissolves very quickly even in cold water. The storage stability in the presence of other components of washing and cleaning agents in many cases reaches that of the perborate tetrahydrate. Another object of the invention is therefore the use of the percarbonate according to the invention as an oxidizing active ingredient in detergents and cleaning agents and in disinfectants.

It is assumed that the properties of the product according to the invention, in addition to the composition, are primarily responsible for the liquid state at room temperature of the coating medium applied in the first stage, which seems to lead to a particularly extensive and at the same time stable coverage of the percarbonate core without the dissolution of the percarbonate in water noticeably. This medium consists predominantly, preferably more than 90% by weight and in particular entirely of a carboxylic acid or a carboxylic acid mixture. The details of the state of matter and the composition are understood to be based on the mixture of the solvent-free constituents, if solvents are additionally used in the encapsulation process.

The carboxylic acids contained in the liquid medium according to the invention are long-chain aliphatic carboxylic acids which have at least 8 carbon atoms and preferably not more than 24 carbon atoms and which can be saturated or unsaturated, but preferably predominantly to completely saturated are. Both synthetic carboxylic acids and, preferably, carboxylic acids of natural origin, such as are obtained by hydrolysis of animal and vegetable fats and oils and fractionation of the carboxylic acid mixture obtained, can be used. The individual chemical individuals can have melting points above 25 ° C, provided that it is ensured that, when mixed with the other constituents of the medium, they produce a liquid phase at 25 ° C. Carboxylic acids which have melting points below 35 ° C., in particular below 32 ° C., are particularly suitable. This group of carboxylic acids includes the long-chain unbranched saturated monocarboxylic acids with 8 to 11 carbon atoms and various branched saturated carboxylic acids, which can also have 12 and more carbon atoms. The latter include, for example, isopalic acid (2-hexyl-1-decanoic acid), which is obtained by oxidation of the corresponding Guerbet alcohol, isostearic acid, a cig carboxylic acid with statistical methyl branching (e.g. Prisorine 3501 from Unichema), and Isononanoic acid (3,5,5-trimethyl-l-hexaπäure). The so-called dimer fatty acids obtainable by dimerization of oleic acid, which are liquid at room temperature, are also suitable. Finally, the unsaturated aliphatic carboxylic acids, which can be both branched and unbranched, should also be mentioned, for example oleic acid, linoleic acid and ricinoleic acid.

Especially in the preferred embodiments of the invention, in which the liquid coating medium comprises more than 90% by weight, in particular entirely, of long-chain aliphatic carboxylic acids, those carboxylic acids are preferably used which already have melting points below 25 ° C. in pure form. Caprylic acid and mixtures which predominantly contain caprylic acid, and oleic acid and mixtures containing these are particularly preferred.

In addition to carboxylic acid, the liquid medium can contain a small amount of further Hü11 substances, provided that these are miscible in type and amount with the carboxylic acids and lead to a liquid phase at room temperature. For the selection of these coating substances it is primarily important that they do not negatively influence the positive effect of the carboxylic acid. For this reason, substances are preferably used which are known per se for the coating of peroxides or other oxidizing agents. Examples include linear primary and secondary alcohols with 8 to 18 carbon atoms, addition products of these alcohols with up to 15 mol of ethylene oxide (EO), esters and alkanolamides of long-chain aliphatic carboxylic acids with 8 to 18 carbon atoms and 1 to 4 carbon atoms mentioned in the alcohol or amine part of the molecule as well as anionic, cationic and other nonionic surfactants, silicone oils and paraffin oils. Finally, the envelope can be aterial complex formers, for example polycarboxylic acids, polyphosphonic acids or aminopolycarboxylic acids or their salts and other auxiliaries and additives, can also be added. When selecting the individual Hü11 substances, it should of course also be ensured that these substances do not cause any disturbances or undesirable side effects when the stabilized percarbonate is used later, for example in detergents and cleaning agents.

The amount of the liquid medium to be applied to the percarbonate largely depends on the desired effects. In general, the storage stability, especially the resistance to moisture, increases with increasing thickness of the coating layer, while the dissolution rate in cold water decreases with increasing layer thickness. In the case of fine grain of percarbonate, larger amounts of coating material are generally necessary than in the case of coarser grain. Therefore, 2 to 15% by weight, in particular 5 to 10% by weight, of liquid medium, based on the stabilized percarbonate, is preferably used.

Percarbonate, which is only coated with the liquid medium, already has a surprisingly high storage stability and quick solubility, but is poorly pourable or even sticky. For this reason, to produce the product according to the invention, a layer of a finely divided solid is powdered, which improves the flowability in a manner known per se. However, only hydrophilic solids which are not detached from the liquid phase of the enveloping medium enclosed below or which have interfering interactions with this phase are suitable according to the invention. Both water-soluble and water-insoluble inorganic or organic substances, in particular organic or inorganic salts, can be used. Examples of suitable solids are sodium carbonate, sodium sulfate, sodium citrate, sodium silicates, water-soluble sheet silicates, for example NaSKSδ from Hoechst, water-insoluble sheet silicates such as hectorite and saponite, zeolites such as zeolite NaA and salts, polymeric carboxylic acids such as copolymers from acrylic acid and maleic acid .

The particle size of the solid used for powdering can be freely selected within wide limits. Good results are achieved with powders, whose average particle diameter is approximately between 2 and 200 μm, in particular between approximately 20 and 200 μm. The amount of powdered solid is kept as low as possible and, depending on the particle size, is between about 1 and about 10% by weight, based on the finished product, in order to achieve sufficient flowability.

The sodium percarbonate to be stabilized according to the invention is generally based on crystalline material. Both high-purity qualities and technical qualities such as are offered by various manufacturers are suitable. The majority of the technical qualities already contain additives which have been incorporated during the manufacturing process or the subsequent granulation of the material in order to improve the crystal properties, stability, free-flowing properties or other properties. These additives, which are on the order of a few percent by weight in technical products, are in most cases inorganic compounds, primarily chlorides, silicates, borates or phosphates of alkali or alkaline earth metals. The technical grade of the active oxygen content, which is 15.3% by weight in the pure sodium percarbonate, is generally between about 12 and about 14.5% by weight. Sodium percarbonate with grain sizes between approximately 0.2 and approximately 0.8 mm is preferably used in the production of the material according to the invention, but it is readily possible to use finer or coarser material. The grain size of the technical grades results either from targeted control of the crystallization process or from subsequent agglomerating granulation of finer material.

The coating layer according to the invention can be applied using a wide variety of methods customary for such measures, it being found that the advantageous properties of the stabilized percarbonate are largely independent of the coating method chosen. For example, the granular percarbonate can be sprayed uniformly in a suitable mixing drum with a solution or suspension of the coating material in a suitable organic solvent and then freed from the solvent using a vacuum and / or elevated temperature. However, the methods in which the granular percarbonate is brought into intimate contact with the liquid medium without volatile solvents. These processes are in turn preferably carried out in solid mixers with spray devices, for example Lödige mixers, in fluidized bed systems or in so-called falling curtain devices. The entire casing is preferably applied in one step. The preferred manufacturing processes are another object of this invention. The application of the liquid medium is followed by powdering with the finely divided solid. This second stage of the process can be carried out in a separate apparatus: however, the powder is preferably applied in the same apparatus, for example a Lödige mixer.

Examples

1. Preparation of the stabilized percarbonate a) An amount of 27.75 kg of sodium percarbonate (technical quality from Degussa, Frankfurt) was placed in a Lödige mixer and, with constant circulation at room temperature, within 20 minutes through a 2.25 mist nozzle kg of a liquid fatty acid mixture sprayed. The mixture consisted of 50% by weight of pre-run fatty acid (Cg / Cio, Edenor ^R V85 KR, Henkel) and technical oleic acid (Edenor ^R LCU). After the fatty acid had been applied, 900 g of powdery anhydrous soda were added and the mixing was continued for a further 5 minutes. The result was a free-flowing fine-grained product.

b) 462.5 g of sodium percarbonate of the same quality as in Example la were placed in a small Lödige mixer, and 37.5 g of a fatty acid mixture were added at room temperature over the course of 2 minutes with constant circulation. This mixture consisted of 50% by weight of Edenor ^R V85 KR and dimer fatty acid (from oleic acid) and was added in a thin stream to the percarbonate in the mixer. Then 25 g of powdery anhydrous soda were added and the mixing continued for 20 minutes. Here too, a free-flowing fine-grained product resulted.

c) (Comparative example according to US 3979318, Example 5)

249 g of percarbonate of the same quality as in Example la were placed in a small Turbula mixer and mixed with 15 g of oleic acid (Edenor ^R LCU) within 15 minutes at room temperature. Then 21 g of finely powdered sodium perborate tetrahydrate were added and mixed for a further 10 minutes. Finally, 15 g of oleic acid were added and mixed in for 15 minutes. The resulting product was very sticky and not free-flowing.

2. Check the release speed

To check whether a sufficiently rapid solution occurs in cold water, 500 ml of water at 25 ° C. were placed in a beaker and stirred with a magnetic stirrer (700 revolutions per minute). After each addition of 2.5 g of the stabilized percarbonate, the increase in conductivity as a function of time was registered with the aid of a conductivity probe. Table 1 shows what proportion of the final conductivity was reached after 120 seconds.

Table 1:

Sample conductivity after 120s

(% of full scale)

Sodium percarbonate (technical), untreated 99

Example la 97

Example lb 99

Example lc 48

The excellent cold water solubility of the percarbonate stabilized according to the invention is evident from the values.

3. Checking the storage stability

The percarbonate was stored in a mixture (weight ratio 20:80) with a universal detergent powder of the following composition:

16% by weight Na dodecylbenzenesulfonate

6% by weight tallow alcohol ethoxylate 20% by weight Na2CÜ3

8.5% by weight sodium silicate

4.5% by weight of acrylic acid-maleic acid copolymer 28% by weight of zeolite A

2 wt .-% tetraacetylethylenediamine (granules 96%) 16 wt .-% small components (including enzyme, optical brightener, perfume), a2SÜ4 and water

The mixtures were stored at 40 ° C. for 8 weeks in closed polyethylene vessels. After this time, the content of active oxygen was determined iodometrically. Table 2 shows what percentage of the active oxygen originally contained was still present after storage.

Table 2:

Sample residual content of active oxygen

(in percent)

Sodium percarbonate (technical), untreated 10

NaB0 x 4H20 60

Example la 51

Example lb 62

It is clear from the values that the percarbonate stabilized according to the invention practically reaches the resistance of the perborate tetrahydrate.

Claims

1. Sodium percarbonate, which is stabilized against decomposition by coating it with a medium which is liquid at 25 ° C. and consists predominantly of a carboxylic acid or a carboxylic acid mixture, the carboxylic acids having at least 8 carbon atoms, and subsequent powdering with an organic or inorganic solid is.

2. Sodium percarbonate according to claim 1, which, based on the end product, is stabilized with 2 to 15% by weight of liquid medium and with 1 to 10% by weight of powder substance.

3. Sodium percarbonate according to one of claims 1 or 2, in which the liquid carboxylic acid or the essential constituents of the liquid carboxylic acid mixture consist of natural fatty acid, preferably of calcium acid.

4. Sodium percarbonate according to one of claims 1 or 2, in which the solid used for powdering is selected from the group of water-soluble inorganic salts, zeolites, water-soluble and water-insoluble phyllosilicates, sodium salts of polycarboxylic acids and mixtures thereof.

5. A process for producing a stabilized sodium percarbonate according to claim 1, in which sodium percarbonate is first mixed with the liquid medium in a mixer with rotating tools and is then immediately mixed with the solid in the same mixer.

6. The method according to claim 5, in which starting from optionally agglomerated sodium percarbonate with an average particle size of 0.2 to 0.8 mm.

7. The method according to claim 5, wherein the particle size of the solid used for powdering is between 20 and 200 microns.

8. Use of stabilized sodium percarbonate according to claim 1 in detergents, cleaning agents or disinfectants.