EP0356700A1 - Granular bleach adduct comprising bleach activators - Google Patents

Abstract

Granular bleaching aids containing bleach activators from the class of N-acyl and O-acyl compounds as well as water-soluble, film-forming polymers which act as granulating aids, also contain 2 to 15 wt.% of a polyvalent carboxylic acid, hydroxycarboxylic acid or ethercarboxylic acid with 3 to 6 carbon atoms per molecule as a stabilizer. To produce the aids, a homogeneous, dry, preliminary mixture containing the bleach activator, the acid and some or all of the polymer granulating aid is prepared. The mixture is then sprayed with water or an aqueous solution of the remaining granulating aid and granulated.

Description

EP 0 037 026-81 (US 4,372,868) discloses a process for producing a readily soluble granulate which contains 90 to 98% by weight of a bleach activator. According to this method, the pulverulent bleach activator is homogeneously mixed with cellulose or starch ether or starch, which is also in powder form, and then sprayed with water or a dilute aqueous solution of the cellulose ether and granulated at the same time. The granules are then dried. Tetraacetylethylenediamine (TAED) is preferably used as the bleach activator and sodium carboxymethylcellulose (CMC) is preferably used as the cellulose ether. After being mixed with granular detergents containing saline in normal storage, the products are characterized by good resistance and quick and complete solubility at medium washing temperatures (45 to 60 ^o C).

Another manufacturing process is described in EP 0 070 474 (US 4,457,858). For this purpose, an aqueous slurry containing the bleach activator and the cellulose ether in a weight ratio of 97: 3 to 93: 7 is spray-dried. In terms of their properties, the products are comparable to those according to EP 0 027 026.

Another production process is described in EP 0 075 818 (US Pat. No. 4,695,397), specifically mixtures of bleach activator are compacted under pressure to form particles with a diameter of 0.5 to 3 mm without the use of water.

It has been shown that the dissolution rate of the known granules at low washing temperatures, in particular in the range between 25 and 40 ^° C., is not yet completely satisfactory. This applies to an increased extent to compacted granules according to EP 0 075 818, which often disintegrate very slowly or incompletely at low washing temperatures. A dispersion aid must therefore be added to the mixtures, such as sodium tripolyphosphate, nitrilotriacetate, sodium sulfate or salts of polymeric or copolymeric carboxylic acids, such as polyacrylate or a copolymer of acrylic acid and maleic acid as the sodium salt. However, these additives also do not significantly improve the dispersing properties, which applies in particular to the (co) polymers. On the other hand, phosphates and nitrilotriacetate are often undesirable from an ecological point of view, while sodium sulfate is a fiber.

The invention described below leads to a significant improvement in the dispersing and solubility properties of the granules. At the same time, the storage stability of the granules in mixtures with washing powder containing saline is increased considerably. It is particularly advantageous that the substances used are completely harmless from an ecological point of view and additionally increase the cleaning effect of the detergents due to their sequestering properties. On the other hand, the required amount of these auxiliaries is so small that the active substance content of the agents is not or only slightly reduced. In addition, this reduction in bleach activator content is more than compensated for by the significantly improved shelf life.

The invention relates to granular bleaching aids containing bleach activators from the class of the N-acyl and O-acyl compounds and at least one pelletizing aid from the class of water-soluble, film-forming polymers, characterized by a content of 2 to 15% by weight of one polyvalent carboxylic acid, hydroxycarboxylic acid or ether carboxylic acid with 3 to 6 carbon atoms in the molecule.

Examples of such polyvalent carboxylic acids are malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, malic acid, tartaric acid, citric acid, diglycolic acid and carboxymethyloxysuccinic acid. Preferred acids are citric acid and carboxymethyl succinic acid. Their proportion, based on the bleach activator granules, is preferably 4 to 12% by weight.

Polyvalent carboxylic acids containing amino groups, such as nitrilotriacetic acid, are unsuitable because they are oxidizable and reduce the bleaching activity.

The known N-acylated amines, diamines, amides, glycolurils, diketopiperazines, hydantoins and acylated polyols and acylated p-hydroxybenzoates or p-hydroxybenzenesulfonates are suitable as bleach activators. Preference is given to tetraacetylmethylene diamine, tetraacetylethylene diamine (TAED), pentaacetyl glucose, hexanoyloxybenzenesulfonate, octanoyloxybenzenesulfonate and nonanoyloxybenzenesulfonate with linear or branched acyl radicals, the sulfonate groups being in the form of sodium. TAED is particularly preferred. The content of bleach activators in the granules is 80 to 96% by weight, preferably 85 to 94% by weight.

Water-soluble, film-forming polymers such as water-soluble cellulose ethers, water-soluble starch or water-soluble starch ethers and mixtures thereof are used as granulation aids. Examples of cellulose ethers are methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, methyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose, carboxymethyl cellulose (as sodium salt) and methyl carboxymethyl cellulose (sodium salt). As a strength comes z. B. Corn starch or depolymerized starch into consideration. Suitable starch ethers are, for example, carboxymethyl starch, hydroxyethyl starch and methyl starch. From this group, sodium carboxymethyl cellulose (CMC) has proven to be particularly suitable.

Also suitable are homopolymeric or copolymeric carboxylic acids, such as polyacrylic acid, polymethacrylic acid, polymaleic acid, copolymers of acrylic acid or methacrylic acid with maleic acid and maleic acid with vinyl methyl ether, these polymeric acids being present as free acids or preferably as sodium salts. Preferred representatives of this group are sodium polyacrylate and sodium salts of acrylic acid-maleic acid copolymers with a weight ratio of acrylic acid: maleic acid of 10: 1 to 1: 1, preferably 7: 1 to 2: 1. These compounds generally have molecular weights of 3,000 to 150,000 , preferably 5000 to 100000.

A third group of film-forming polymers are carbon chain polymers with nonionic hydrophilic groups or polyether groups. Examples include polyvinyl alcohol, partially saponified polyvinyl acetate, polyvinyl pyrrolidone, polyacrylamide and polyethylene glycol ether.

Mixtures of film-forming polymers of the aforementioned groups are used, for. B. a mixture of CMC or methyl cellulose with polyacrylate or with an acrylic acid-maleic acid copolymer or mixtures of one of the latter two polymers with polyethylene glycol ethers.

The granulation aid content of the granules is 0.3 to 5% by weight, preferably 0.5 to 3% by weight. Despite this reduced content of granulating aids compared to the information in EP-B 0 037 026, the agents according to the invention are notable for good grain stability and a further improved storage capacity resistance in mixtures with detergents containing peroxides and washing alkalis.

The granules can contain small amounts of moisture, for example up to 3% by weight, preferably less than 2% by weight. In contrast to known granules, this water content is not critical, i. H. even a slightly increased water content does not lead to a significant reduction in shelf life. This proves to be particularly valuable if the agents are stored in unfavorable climatic conditions, such as high air humidity and elevated temperature.

The production can be carried out by means of conventional granulation processes and granulation devices. The procedure is preferably such that an intimate, dry mixture of the bleach activator and the polyvalent carboxylic acid is first prepared and sprayed with an aqueous solution of the granulating aid in a granulating device. Depending on the viscosity, the concentration of the aqueous solution can contain 2 to 20% by weight of the granulation aid. The procedure can also be such that a dry mixture of all components, including the powdered granulation aid or part thereof, is first prepared and then sprayed with water or an aqueous solution which contains the rest of the granulation aid in solution. Such a procedure is particularly recommended when the aqueous solutions of the granulating aid swell strongly and become so highly viscous that they are difficult to spray and can be distributed in the mixture to be granulated. This can e.g. B. then the case when carboxymethyl cellulose in a concentration of more than 1 to 2 wt .-% should be used as a granulating aid. In order to introduce larger amounts of granulation aid, would be in In these cases, comparatively large amounts of water are required, which would have to be removed by drying during the granulation or afterwards.

If the proportion of the granulating aid is in the range from 0.3 to 1.5% by weight, in particular 0.5 to 1% by weight, the first-mentioned procedure, i. H. the introduction of the granulating aid as an aqueous solution is preferred.

During the granulation, additives such as dyes or color pigments can also be mixed in or introduced via the aqueous granulation liquid. Small amounts of further, oxidation-stable complexing agents and stabilizers for per compounds can also be mixed in this process step. Examples of these are salts of polyphosphonic acids, such as 1-hydroxyethane-1,1-diphosphonate, ethylene diamine tetramethylene phosphonate and diethylene triamine pentamethylene phosphonate, each in the form of the sodium salt. The proportion of these additives can be up to 2% by weight, generally up to 0.5% by weight, based on the granules.

The water content of the granules is then reduced to less than 3, preferably less than 2 and in particular less than 1.5% by weight. The excess water can be removed by drying with the addition of heat, the temperature of the granules advantageously not exceeding 80 ^° C. and below the melting temperature of the bleach activator and the carboxylic acid. Dryers that do not adversely change the granular structure of the product are suitable, for example tray, vacuum or fluidized bed dryers.

It is also possible to add to the granules intended for use in detergents or in washing processes during the granulation process those substances which are usually very small amounts are added to the detergents separately in a special mixing process. These additives are those which are inactivated or lost in conventional detergent preparation, in particular in hot spray drying, such as foam inhibitors and fragrances. Suitable foam inhibitors are customary known defoamers, preferably polysiloxanes, and mixtures thereof with microfine silica. Examples include polydimethylsiloxane with a content of approx. 1 to 10% by weight, preferably 2 to 4% by weight, based on the finished granulate. The defoamer can be added in the first mixing stage; however, the defoamer can also be dispersed in the granulating liquid which, in order to avoid segregation processes, should contain a part of the granulating aid in this case.

The granules produced in the manner indicated have a favorable grain spectrum. Any coarse and fine fractions that are present can be screened off and returned to the process after the coarse fractions have been ground. The granules are easy to pour, non-adhesive and are characterized by superior storage stability. Even at low washing temperatures such as those of 25 to 40 ^o C they decay very rapidly and completely, so that the full bleaching power is also under such washing conditions within a short time fully available. They can be used to advantage in detergents, sheet metal agents, oxidizers and disinfectants and retain their good properties even when mixed with the active ingredients contained in these agents.

Examples example 1

Tetraacetylethylenediamine (TAED) with an average grain size of 0.01 to 0.8 mm was used as the bleach activator. The grain fraction between 0.8 and 1.6 mm was 5% by weight, the fraction below 0.01 mm 10% by weight. The abbreviation GT used in the following stands for parts by weight. 88.1 pbw of the powdery bleach activator were dry mixed with 10.4 pbw of citric acid (particle size 0.05 to 0.5 mm) in a horizontally rotatable mixer equipped with mixing and chopping tools attached to a rotating shaft. Over the course of 4 minutes, 10 parts by weight of sodium polyacrylate (MW = 10000) in 10% by weight aqueous solution were sprayed onto the homogeneous, constantly kept mixture. The granulation process was then continued for 1 minute. The still moist granules were dried in a fluidized bed dryer with air at 50 ^° C. to a water content of 1% by weight. The content of the granules was thus
88.1 wt% TAED
10.4% by weight of citric acid
0.5% by weight polyacrylate
1.0 wt% water.
92% by weight of the granules had a grain size of 0.1 to 1.2 mm. The rest was coarse and very fine, which were screened off.

To test the storage stability, 1.7% by weight (corresponding to 1.5% by weight TAED) of the granules were mixed with 98.3% by weight of a commercially available, phosphate-reduced granular detergent containing 21.5% by weight sodium perborate. tetrahydrate, intimately mixed. Each 400 g of the powder mixture were filled in customary printed cardboard packs and stored in a climatic cell at 30 ^o C and 80 ^o relative air humidity.

The determination of the solution properties and bleaching activity was carried out under practical conditions in a household washing machine in the presence of clean test laundry (the latter in order to avoid uncontrollable influences of individual soiling). In accordance with the metering instructions, 1.5 measuring beakers were filled into the induction chamber and the washing process started. A first sample was taken at an alkali temperature of 30 ^° C. After reaching the final temperature of 40 ^o C, further samples were taken at intervals and the peracid content was determined analytically.

Products were compared for comparison
a) EP 0 037 026, example 1
b) EP 0 075 818, example 3 (W3)
used, in both experiments the content of TAED in the mixture was also set to 1.5% by weight.

The following results were achieved: Storage stability example 1 Comparison a Comparison b Beginning 100% 99% 100% 4 weeks 100% 87% 94% 8 weeks 96% 79% 92% Bleaching activity Alkali temperature example Comparison a Comparison b 30 ^o reached 92% 72% 55% 40 ^o reached 100% 88% 78% 40 ^o after 3 min. 100% 95% 40 ^o after 5 min 100%

Claims (10)

1. Granular bleaching aids containing bleach activators from the class of the N-acyl and O-acyl compounds and at least one pelletizing aid from the class of water-soluble, film-forming polymers, characterized by a content of 2 to 15% by weight of a polyvalent carboxylic acid, Hydroxycarboxylic acid or ether carboxylic acid with 3 to 6 carbon atoms in the molecule. 2. Composition according to claim 1, characterized in that the carboxylic acid consists of citric acid. 3. Composition according to claims 1 or 2, characterized in that the carboxylic acid content is 4 to 12 wt .-%. 4. Composition according to one or more of the preceding claims, characterized in that the bleach activator consists of tetraacetylethylene diamine and is present in proportions of 80 to 96 wt .-%. 5. Composition according to one or more of the preceding claims, characterized in that the granulating aid consists of sodium carboxymethyl cellulose, polyacrylic acid or a copolymer of polyacrylic acid with maleic acid in a ratio of 10: 1 to 1: 1 or their sodium salts. 6. Composition according to claim 5, characterized in that the proportion of the granulating aid is 0.3 to 5% by weight. 7. Composition according to one or more of claims 1 to 6, characterized in that its water content is less than 3 wt .-%, preferably less than 2 wt .-%. 8. A process for the preparation of the agent according to one or more of claims 1 to 7, characterized in that a homogeneous dry mixture of the bleach activator and the polybasic carboxylic acid is sprayed and granulated with an aqueous solution of the granulating aid. 9. A process for the preparation of the agent according to one or more of claims 1 to 7, characterized in that a dry mixture is prepared which contains the bleach activator, the carboxylic acid and part or all of the granule auxiliary, whereupon the mixture is mixed with water or an aqueous solution of the remaining amount of the granulating aid is sprayed and granulated. 10. The method according to claim 8 or 9, characterized in that a dye or pigment is added.