US20050148484A9

US20050148484A9 - Enclosed bleach activators

Info

Publication number: US20050148484A9
Application number: US10/343,877
Authority: US
Inventors: Horst-Dieter Speckmann; Bernd Larson; Joerg Poethkow; Peter Schmiedel; Lars Zuechner; Manfred Schreiber; Georg Borchers; Oliver Mogck; Frank Weinelt
Original assignee: Henkel AG and Co KGaA
Current assignee: Henkel AG and Co KGaA
Priority date: 2000-08-04
Filing date: 2001-07-25
Publication date: 2005-07-07
Also published as: WO2002012426A1; DE10038832A1; AU2001289747A1; US20040067863A1; DE50111695D1; EP1305386B1; EP1305386A1; ES2277940T3; ATE348870T1; JP2004517160A

Abstract

The aim of the invention is to improve the stability in storage of bleach activators of the quaternized amino alkyl nitrile type. To this end, the invention provides that a particle containing these bleach activators is enclosed in the most complete possible manner by an enclosing material.

Description

The present invention relates to enclosed bleach activators of the quaternized aminoalkylnitrile type.
As well as containing ingredients which are indispensable for the washing process, such as surfactants and builder materials, detergents usually contain further constituents which can be summarized under the term washing auxiliaries and include diverse groups of active substances, such as foam regulators, antiredeposition agents, bleaches and color transfer inhibitors. Auxiliaries of this type also include substances which aid the surfactant performance as a result of oxidative degradation of soilings located on the textile or those in the liquor. Analogous statements also apply to cleaners for hard surfaces. For example, inorganic peroxygen compounds, in particular hydrogen peroxide, and solid peroxygen compounds which dissolve in water to liberate hydrogen peroxide, such as sodium perborate and sodium carbonate perhydrate, have been used for a long time as oxidizing agents for disinfection and bleaching purposes. The oxidative effect of these substances greatly depends in dilute solutions on the temperature; thus, for example with H₂O₂or perborate in alkaline bleaching liquors, a sufficiently rapidly bleaching of soiled textiles only takes place at temperatures above about 60° C. At lower temperatures it is possible to improve the oxidative effect of the inorganic peroxygen compounds by adding so-called bleach activators, for which numerous proposals, primarily from the classes of substance of N- or O-acyl compounds, for example polyacylated alkylenediamines, in particular tetraacetylethylene-diamine, acylated glycolurils, in particular tetraacetylglycoluril, N-acylated hydantoins, hydrazides, triazoles, hydrotriazines, urazoles, diketopiperazines, sulfurylamides and cyanurates, and also carboxylic anhydrides, in particular phthalic anhydride, carboxylic esters, in particular sodium nonanoyloxybenzenesulfonate, sodium isononanoyloxy-benzenesulfonate and acylated sugar derivatives, such as pentaacetylglucose, have become known in the literature. The addition of these substances can increase the bleaching action of aqueous peroxide liquors such that even at temperatures below 60° C. essentially the same effects arise as with the peroxide liquor on its own at 95° C.
European patent application 0 464 880 discloses bleach-enhancing cationic nitriles of the general formula R′R″R″′N⁺—CR₁R₂—CN X⁻, in which R₁and R₂is hydrogen or a substituent with at least one carbon atom, R′ is a C_1-24-alkyl, alkenyl or alkyl ether group or a group —CR₁R₂—CN, and R″ and R″′ is in each case a C_1-24-alkyl or hydroxyalkyl group, and the counteranion X⁻ is an organic sulfonate, an organic sulfate or a carboxylate.
International patent application WO 98/23719 discloses that compounds of the general formula R¹R²R³N⁺CH₂CN X⁻, in which R¹, R²and R³, independently of one another, is an alkyl, alkenyl or aryl group having 1 to 18 carbon atoms, where the groups R²and R³may also be part of a heterocycle including the N atom and optionally further heteroatoms, and X is a charge-balancing anion, can be used as activators for, in particular, inorganic peroxygen compounds in aqueous dishwashing solutions. This provides an improvement in the oxidative and bleaching effect in particular of inorganic peroxygen compounds at low temperatures below 80° C., in particular in the temperature range from about 15° C. to 55° C. However, particularly in combination with further ingredients of detergents and cleaners, the cationic nitriles are normally not very storage-stable and, in particular, are sensitive to moisture.
The present invention, with which this problem can be solved, relates to particles containing bleach activator of the general formula (I),

in which R¹is —H, —CH₃, a C_2-24-alkyl or -alkenyl radical, a substituted C_2-24-alkyl or -alkenyl radical having at least one substituent from the group —Cl, —Br, —OH, —NH₂, —CN, an alkyl- or alkenylaryl radical with a C_1-24-alkyl group, or is a substituted alkyl- or alkenylaryl radical with a C_1-24-alkyl group and at least one other substituent on the aromatic ring, R²and R³, independently of one another, are chosen from —CH₂—CN, —CH₃, —CH₂—CH₃, —CH₂—CH₂—CH₃, —CH(CH₃)—CH₃, —CH₂—OH, —CH₂—CH₂—OH, —CH(OH)—CH₃, —CH₂—CH₂—CH₂—OH, —CH₂—CH(OH)—CH₃, —CH(OH)—CH₂—CH₃, —(CH₂CH₂—O)_nH where n=1, 2, 3, 4, 5 or 6, R⁴and R⁵, independently of one another, have an abovementioned meaning given for R¹, R²or R³, and X is a charge-balancing anion, which are enclosed in the most complete manner possible with an enclosing material.
Compounds according to formula I can be produced by known methods or ones based on these, as have been published, for example, in said patent literature or by Abraham in Progr. Phys. Org. Chem. 11 (1974), p. 1ff, or by Arnett in J. Am. Chem. Soc. 102 (1980), p. 5892ff.
Preference is given to the use of compounds according to formula I in which R¹, R²and R³are identical. Of these, preference is given to those compounds in which said radicals are methyl groups. On the other hand, preference is also given to those compounds in which at least 1 or 2 of said radicals are methyl groups and the others have two or more carbon atoms.
The anions X⁻ include, in particular, the halides, such as chloride, fluoride, iodide and bromide, nitrate, hydroxide, phosphate, hydrogen phosphate, dihydrogen phosphate, pyrophosphate, metaphosphate, hexafluoro-phosphate, carbonate, hydrogen carbonate, sulfate, hydrogen sulfate, C_1-20-alkyl sulfate, C_1-20-alkyl-sulfonate, optionally C_1-18-alkyl-substituted aryl-sulfonate, chlorate, perchlorate and/or the anions of C_1-24-carboxylic acids, such as formate, acetate, laurate, benzoate or citrate, alone or in any desired mixtures.
Preference is given to compounds according to formula I in which X⁻ is chloride, sulfate, hydrogen sulfate, ethosulfate, C_12/18—, C_12/16— or C_13/15-alkyl sulfate, lauryl sulfate, dodecylbenzenesulfonate, toluenesulfonate, cumenesulfonate, xylenesulfonate or methosulfate or mixtures thereof. Toluenesulfonate and cumenesulfonate are understood here as meaning the anion of the ortho, meta or paraisomers of methylbenzenesulfonic acid and isopropylbenzenesulfonic acid, respectively, and any desired mixtures thereof. para-isopropylbenzenesulfonic acid is particular preferred.
The compound according to general formula I can be used in solid form as it is or formulated in particulate form, i.e. applied to an organic and/or inorganic carrier material, as starting material for the enclosure according to the invention. In this connection, the compound according to formula (I) can be applied to the carrier material by stirring the carrier material into a solution of the compound according to formula I, as formed during the course of its production, and stripping off the optionally aqueous solvent under reduced pressure, if desired at elevated temperature. However, it is also possible to spray the solution of the compound according to formula I onto the carrier material and, during this operation or optionally subsequently to it, subject it to a drying process. In this connection it is preferred if the particles resulting from the formulating process have a diameter in the range from 0.4 mm to 3 mm. Suitable carrier materials are all substances which do not interact in an unreasonably negative manner with the compound according to formula I, for example alkali metal cumenesulfonate, surfactants, organic acids and polymers, alkali metal carbonates, alkali metal sulfates, alkali metal hydrogen sulfates, alkali metal hydrogen carbonates, alkali metal phosphates, alkali metal dihydrogen phosphates, dialkali metal hydrogen phosphates and alkali metal silicates and mixtures thereof. Preference is given to using those carrier materials whose internal surface area is in the range from 10 m²/g to 500 m²/g, in particular 100 m²/g to 450 m²/g. The silicatic carrier materials particularly suitable for the purposes of the present invention include, for example, alkali metal silicates, and also silicas, silica gels and clays, and mixtures thereof. However, the carrier material is preferably free from zeolites. In addition to the silicate component, the silicate-containing carrier material optionally comprises further particulate inert constituents which do not unreasonably impair the stability of the compounds according to the formula I. Silicas which have been produced by a thermal process (flame hydrolysis of SiCl₄) (so-called pyrogenic silicas) are equally suitable for use as are silicas produced by wet methods. Silica gels are colloidal silicas with an elastic to solid consistency and a substantially loose pore structure, resulting in a high liquid-uptake capacity. They can be produced by the action of mineral acids on waterglass. Clays are naturally occurring crystalline or amorphous silicates of aluminum, iron, magnesium, calcium, potassium and sodium, for example kaolin, talc, pyrophyllite, attapulgite, sepiolite, montmorillonite and bauxite. The use of aluminum silicate as a carrier material or as a component of a carrier material mixture is also possible. The carrier material preferably has particle sizes in the range from 100 μm to 1.5 μm.
The coating materials should have proven as far as possible to be substantially chemically inert toward the bleach activator, i.e. the degradation rate for the particles containing the bleach activator according to formula (I) to be used according to the invention, which are stored for about 4 months, should be as low as possible. In addition, the coating materials must be sufficiently rapidly soluble in water or aqueous solutions so that the granules, as constituents of detergents or cleaners, upon use thereof in corresponding aqueous detergent or cleaner solutions, release the bleach activator at the desired point in time, or over the desired period of time. In addition, the use of the correspondingly enclosed particles in textile detergents often results in a greater avoidance of color damage of textiles washed therewith than does the use of the pure substance according to formula (I).
Suitable coating materials for the purposes of this invention are, in particular, inorganic salts, such as alkali metal sulfates, alkali metal chlorides, alkali metal silicates, alkali metal phosphates and alkali metal phosphonates, alkaline earth metal sulfates and alkaline earth metal silicates, paraffin waxes, water-soluble saccharide-based polymeric compounds, such as starch or starch derivatives or cellulose derivatives, polymeric alcohols, for example polyvinyl alcohols and polyethylene glycols, homo- and copolymeric polycarboxylates, polyesters of dicarboxylic acids and optionally oligo- or polymeric alcohols, nonionic surfactants, anionic surfactants, hydroxy carboxylic acids, such as glycolic acid and citric acid, and/or fatty acids.
In said inorganic salts, sodium is the preferred alkali metal ion and magnesium is the preferred alkaline earth metal ion.
Paraffin wax generally represents a complex substance mixture without a sharp melting point. For characterization, determination is usually made of its melting range by differential thermal analysis (DTA), as described in “The Analyst” 87 (1962), 420, and/or of its solidification point. This is understood as meaning the temperature at which molten material converts from the liquid state to the solid state by slow cooling. Preference is given to using waxes which solidify in the range from 20° C. to 70° C. Here, it must be taken into consideration that paraffin wax mixtures which appear solid at room temperature may also contain varying proportions of liquid paraffin. In the paraffin waxes which are particularly suitable for use according to the invention, the liquid fraction at 40° C. is as high as possible without being 100% at this temperature. Particularly preferred paraffin wax mixtures have, at 40° C., a liquid fraction of at least 50% by weight, in particular from 55% by weight to 80% by weight, and, at 60° C., a liquid fraction of at least 90% by weight. In addition, it must be ensured that the paraffins contain the smallest possible volatile fractions. Preferred paraffin waxes comprise less than 1% by weight, in particular less than 0.5% by weight, of fractions which can be vaporized at 110° C. and atmospheric pressure. Paraffin waxes which are particularly suitable for use according to the invention can be obtained, for example, under the trade names Lunaflex® from Fuller, and Deawax® from DEA Mineralöl AG.
The water-soluble starch or cellulose derivatives which can be used as coating materials include, in particular, starch ethers and cellulose ethers. Examples of cellulose ethers are methylcellulose, ethylcellulose, hydroxyethylcellulose, methylhydroxyethylcellulose, methylhydroxypropylcellulose and carboxymethylcellulose, which is normally used as the sodium salt. Suitable as starch is, for example, depolymerized starch. Suitable starch ethers are, for example, carboxymethylstarch, hydroxyethylstarch and methyl-starch. Sodium carboxymethylcellulose and starch have proven to be particularly suitable. It is also particularly advantageous to use gelatin as coating material.
Polyvinyl alcohols are not accessible by direct polymerization methods since the base monomer vinyl alcohol required therefor does not exist. Polyvinyl alcohols are therefore produced via polymer-analogous reactions by hydrolysis, but industrially, in particular, by alkali-catalyzed transesterification of polyvinyl acetates with alcohols (for example methanol) in solution. Polyvinyl alcohols which are preferably used according to the invention, which are usually supplied commercially as white-yellowish powders or granules, have molar masses in the range from 3000 g/mol to 320,000 g/mol, in particular 8000 g/mol to 200,000 g/mol (corresponding to degrees of polymerization in the range from about 75-8000, in particular about 200 to 5000). They preferably have degrees of hydrolysis of from 20% by weight to 100% by weight, in particular from 30% by weight to 90% by weight. Expressed in another way, these are completely or partially saponified polyvinyl alcohol esters, in particular polyvinyl acetates, with a residual content of acyl groups, in particular acetyl groups, up to about 80% by weight, in particular from 10% by weight to 70% by weight. The polyvinyl alcohols can be further characterized by quoting the degree of polymerization of the starting polymer, the degree of hydrolysis, the saponification number and/or the solution viscosity. Transformation temperatures of the polyvinyl alcohols are dependent on the acetyl group content, the distribution of the acetyl groups along the chain and the tacticity of the polymers. Completely saponified polyvinyl alcohols have a glass transition temperature of 85° C., the value for partially saponified (87-89%) products being considerably lower at about 58° C. Polyvinyl alcohols, which normally have a density of about 1.2-1.3 g/cm³, are, depending on the degree of hydrolysis, normally soluble in water and strongly polar organic solvents, such as formamide, dimethylformamide and dimethyl sulfoxide, and they are not attacked by (chlorinated) hydrocarbons, esters, fats and oils. Polyvinyl alcohols are classified as toxicologically acceptable and are biodegradable. Further suitable coating materials are polyethylene glycols which have, for example, a relative molecular mass between 10,000 and 20,000. It is also possible to use homo- and copolymeric carboxylates, such as polyacrylates, polymethacrylates and in particular copolymers of acrylic acid with maleic acid, preferably those containing about 50% by weight to 10% by weight of maleic acid. The relative molecular mass of these homopolymers is generally between 1000 and 100,000, that of the copolymers is between 2000 and 200,000, preferably 50,000 to 120,000, based on free acid. A particularly preferred acrylic acid-maleic acid, copolymer has a relative molecular mass of from 50,000 to 100,000. Further suitable compounds of this class are copolymers of acrylic acid or methacrylic acid with vinyl ethers, such as vinyl methyl ethers, in which the proportion of acid is preferably at least 50% by weight.
A further embodiment of the invention arises through the use of so-called host molecules or compounds which, due to their structure or arrangement, can protect bleach activators which are able to enclose molecules such as said bleach activators optionally in their inside. A preferred cage compound is cyclodextrin. The bleach activator according to formula (I) and cyclodextrin are particularly advantageously used in a molar ratio of from 1:1 to 1:2.
Among the polyesters used as coating materials, preference is given to those which impart soil-repelling properties to the laundry fibers and which, if present during the washing operation, aid the soil release capacity of the other detergent constituents. These are often referred to as soil release active substances or, due to their ability to give the treated surface of the fibers a soil-repelling property, as soil repellants. The same effect can also be observed when they are used in cleaners for hard surfaces. Due to their chemical similarity to polyester fibers, particularly effective and therefore preferred soil release active substances, which can, however, also exhibit the desired effect with fabrics or surfaces made of another material, are copolyesters which contain dicarboxylic acid units, alkylene glycol units and polyalkylene glycol units. Soil release copolyesters of said type and also their use in detergents have been known for a long time. Thus, for example, German Laid-Open Specification DT 16 17 141 describes a washing process using polyethylene terephthalate-polyoxyethylene glycol copolymers. German Laid-Open Specification DT 22 00 911 relates to detergents which comprise nonionic surfactant and a copolymer of polyoxyethylene glycol and polyethylene terephthalate. German Laid-Open Specification DT 22 53 063 mentions acidic textile finishing agents which comprise a copolymer of a dibasic carboxylic acid and an alkylene or cycloalkylene polyglycol and optionally an alkylene or cycloalkylene glycol. Polymers of ethylene terephthalate and polyethylene oxide terephthalate in which the polyethylene glycol units have molecular weights of from 750 to 5000 and the molar ratio of ethylene terephthalate to polyethylene oxide terephthalate is 50:50 to 90:10, and their use in detergents is described in German patent specification DE 28 57 292. Polymers with a molecular weight of 15,000 to 50,000 of ethylene terephthalate and polyethylene oxide terephthalate, where the polyethylene glycol units have molecular weights of from 1000 to 10,000 and the molar ratio of ethylene terephthalate to polyethylene oxide terephthalate is 2:1 to 6:1, can, according to German Laid-Open Specification DE 33 24 258, be used in detergents. European patent EP 066 944 relates to textile treatment agents which comprise a copolyester of ethylene glycol, polyethylene glycol, aromatic dicarboxylic acid and sulfonated aromatic dicarboxylic acid in certain molar ratios. European patent EP 0 185 427 discloses methyl- or ethyl group end-capped polyesters containing ethylene terephthalate and/or propylene terephthalate and polyethylene oxide terephthalate units and detergents which comprise such a soil release polymer. European patent EP 0 241 984 relates to a polyester which, in addition to oxyethylene groups and terephthalic acid units, also contains substituted ethylene units and glycerol units. European patent EP 0 241 985 discloses polyesters which, in addition to oxyethylene and terephthalic acid units, comprise 1,2-propylene, 1,2-butylene and/or 3-methoxy-1,2-propylene groups and glycerol units and are end-capped with C₁- to C₄-alkyl groups. European patent specification EP 0 253 567 relates to soil release polymers with a molar mass of from 900 to 9000 of ethylene terephthalate and polyethylene oxide terephthalate, where the polyethylene glycol units have molecular weights of from 300 to 3000 and the molar ratio of ethylene terephthalate to polyethylene oxide terephthalate is 0.6 to 0.95. European patent application EP 0 272 033 discloses polyesters with polypropylene terephthalate and polyoxyethylene terephthalate units which are end-capped at least in part by C_1-4-alkyl or acyl radicals. European patent EP 0 274 907 describes sulfoethyl end-capped terephthalate-containing soil release polyesters. In European patent application EP 0 357 280, soil release polyesters with terephthalate, alkylene glycol and poly-C_2-4-glycol units are produced by sulfonation of unsaturated end groups. International patent application WO 95/32232 relates to soil release polyesters of the general formula
X—(O—(CHR—)_a)_b[—OC—Ph—CO—(O—(CHR—)_o)_p]_yO—Y (II)
in which

- a is a number from 2 to 8,
- b is a number from 1 to 300,
- o is a number from 2 to 8,
- p is a number from 1 to 300 and
- y is a number from 1 to 500,
- Ph is an o-, m- or p-phenylene radical which can carry 1 to 4 substituents chosen from alkyl radicals having 1 to 22 carbon atoms, sulfonic acid groups, carboxyl groups and mixtures thereof,
- R is chosen from hydrogen, an alkyl radical having 1 to 22 carbon atoms and mixtures thereof, and
- X and Y, independently of one another, are chosen from hydrogen, alkyl- and arylmonocarboxylic acid radicals having 5 to 32 carbon atoms, hydroxy monocarboxylic acid radicals having 2 to 22 carbon atoms and a degree of oligomerization of from 1 to 100, and dicarboxylic half-ester radicals whose second carboxylic acid group is esterified by an alcohol A-(OCHZCH₂)_d—OH, in which A is an alkyl or alkenyl radical having 8 to 22 carbon atoms, Z is hydrogen or an alkyl radical having 1 to 2 carbon atoms and d is a number from 1 to 40, with the proviso that X and Y are not hydrogen at the same time, if R is hydrogen or an alkyl radical with 1 carbon atom, a and/or o is 2 and b and/or p is 1.

It is likewise also possible to use, as coating materials, nonionic surfactants, which are understood as meaning, in particular, polyalkoxylates of fatty alcohols solid at room temperature, and anionic surfactants, in particular C₉-C₁₃-alkylbenzenesulfonates, C₁₂-C₁₈-fatty alcohol sulfates, and C₁₂-C₁₈-fatty acids and salts thereof, and mixtures of these, where the anionic surfactants are usually in the form of the alkali metal salts, in particular sodium salts.
The particles according to the invention have a content of bleach activator according to formula (I) of preferably at least 40% by weight and in particular from 50% by weight to 92% by weight; the coating material is present in the granules preferably in amounts up to 60% by weight, in particular from 3% by weight to 50% by weight and particularly advantageously from 10% by weight to 25% by weight, based on the sum of bleach activator and coating material.
As a result of the production, the granules can contain small amounts of free water not bound as water of crystallization or in a comparable form. These should be as low as possible, the amounts which may normally be tolerated being up to about 5% by weight. However, the granules preferably contain 0 to 3% by weight of water.
The invention further provides a method for producing granules containing enclosed bleach activator according to formula (I) by spraying the bleach activator according to formula (I) present in solid, in particular pulverulent, form, if desired in a mixture with binder and/or solid filler or in the form of preproduced granules, with an organic enclosing material which is liquid or liquefied by heating, where the material to be enclosed is, preferably, kept in motion, for example by being in a fluidized bed, a mixer or granulator. In the case of the latter, it is possible, particularly when binders are present or the enclosing material also has binder properties, to adjust the desired particle size or particle size distribution of the resulting enclosed particles in a simple manner essentially through the duration of mixing or granulation. Organic and also inorganic enclosing materials such as the alkali metal or alkaline earth metal salts mentioned, particularly when they are solid at room temperature, can also be applied in this way if they are converted beforehand into a solution or at least a pumpable and sprayable slurry, where water is the preferred solvent or slurrying agent, and if desired the solvent or slurrying agent can then at least partially be removed again subsequently to the enclosure operation by a drying step. The drying step can also, particularly when the enclosure is carried out in a fluidized bed with introduced air at temperatures of preferably 25° C. to 80° C. and in particular 45° C. to 75° C., be carried out at the same time as the enclosure operation.
A further embodiment of the method according to the invention consists in introducing the bleach activator according to formula (I) into enclosing material liquefied by heating, cooling the resulting mixture to below the melting point or the softening point of the enclosing material and, during this or subsequently, converting it to granules in a manner known in principle, by, for example, pelleting, pastilling, extrusion or, if desired, grinding. Preferred enclosing materials in this process variant are the abovementioned waxes, polyesters and fatty acids, in particular stearic acid.
If the enclosed granules have an excessive tendency to adhere, they can be after-treated with customary powdering agents, for example finely divided silica or zeolites.
Enclosed particles according to the invention or enclosed particles produced by the method according to the invention preferably have an average particle diameter in the range from 0.2 mm to 3 mm, in particular 0.4 mm to 1.8 mm. They are stable upon storage over prolonged periods, in particular against hydrolysis of the bleach activator according to formula (I), and are used in, in particular particulate, detergents and cleaners preferably in amounts such that these compositions have contents of from 0.1% by weight to 10% by weight, in particular from 0.2% by weight to 7% by weight of bleach activator according to formula (I).

Claims

1-14. (canceled)

15. A method for producing particles containing bleach activator according to formula (I):

wherein R¹is —H, —CH₃, a C_2-24-alkyl or -alkenyl radical, a substituted C_2-24-alkyl or -alkenyl radical having at least one substituent from the group —Cl, —Br, —OH, —NH₂, —CN, an alkyl- or alkenylaryl radical with a C_1-24-alkyl group, or a substituted alkyl- or alkenylaryl radical with a C_1-24-alkyl group and at least one other substituent on the aromatic ring, R²and R³, independently of one another, are —CH₂—CN, —CH₃, —CH₂—CH₃, —CH₂—CH₂—CH₃, —CH(CH₃)—CH₃, —CH₂—OH, —CH₂-CH₂—OH, —CH(OH)—CH₃, —CH₂—CH₂—CH₂—OH, —CH₂—CH(OH)—CH₃, —CH(OH)—CH₂—CH₃, —(CH₂CH₂—-O)_nH, n=1, 2, 3, 4, 5 or 6, R⁴and R⁵, independently of one another, have the meanings of R¹, R², or R³, and X is a charge-balancing anion, the bleach activator according to formula I) being in solid, particulate form, said bleach activator particles optionally comprising a binder, filler, or mixture thereof, said method comprising the steps of spraying the particles of bleach activator with a liquid coating material, while keeping the particles in motion, until the particles are effectively covered.

16. The method of claim 15, carried out in a fluidized bed, a mixer, or a granulator.

17. The method of claim 15, wherein the coating material comprises a material selected from the group consisting of alkali metal sulfates, alkali metal chlorides, alkali metal silicates, alkali metal phosphates, alkali metal phosphonates, alkaline earth metal sulfates, alkaline earth metal silicates, paraffin waxes, water-soluble saccharide-based polymeric compounds, starch, starch derivatives, cellulose, cellulose derivatives, polyvinyl alcohols and polyethylene glycols, homo- and copolymeric polycarboxylates, polyesters of dicarboxylic acids and optionally oligoalcohols, nonionic surfactants, anionic surfactants, glycolic acid, citric acid, and mixtures thereof.

18. The method of claim 15, wherein the coating material is selected from the group consisting of inorganic salts, paraffin waxes, water-soluble saccharide based polymeric compounds, starch, starch derivatives, cellulose, cellulose derivatives, polymeric alcohols, oligoalcohols, nonionic surfactants, anionic surfactants, hydroxy carboxylic acids, fatty acids, and mixtures thereof.

19. The method of claim 16, wherein the liquid coating material is a solution or a pumpable and sprayable slurry.

20. The method of claim 19, wherein the liquid of the coating material is at least partially removed during or subsequent to the spraying step by a drying step.

21. The method of claim 15, wherein the coating material is liquefied by heating and the coated bleach activator particles are cooled to below the melting point or the softening point of the coating material and granulated.

22. The method of claim 21, wherein the coating material comprises wax, polyester, or fatty acid.

23. The method of claim 22, wherein the coating material comprises stearic acid.

24. A particle comprising bleach activator or activators of the formula (I):

wherein R¹is —H, —CH₃, a C_2-24-alkyl or - alkenyl radical, a substituted C_2-24-alkyl or -alkenyl radical having at least one substituent from the group —Cl, —Br, —OH, —NH₂, —CN, an alkyl- or alkenylaryl radical with a C_1-24-alkyl group, or a substituted alkyl- or alkenylaryl radical with a C_1-24-alkyl group and at least one other substituent on the aromatic ring, R²and R³, independently of one another, are —CH₂—CN, —CH₃, —CH₂—CH₃, —CH₂—CH₂—CH₃, —CH(CH₃)—CH₃, —CH₂—OH, —CH₂—CH₂—OH, —CH(OH)—CH₃, —CH₂—CH₃—CH₂—OH, —CH₂—CH(OH)—CH₃, —CH(OH)—CH₂—CH₃, or —(CH₂CH₂—O)_nH, n=1, 2, 3, 4, 5 or 6, R⁴and R⁵, independently of one another, have the meanings of R¹, R²or R³, and X is a charge-balancing anion, and wherein the bleach activator or activators are enclosed in the most complete manner possible by a coating material.

25. The particle of claim 24, comprising at least 40% by weight of the bleach activator or activators according to formula (I) and up to 60% by weight of the coating material.

26. The particle of claim 25, comprising from 50% by weight to 92% by weight of the bleach activator or activators according to formula (I) and from 8% by weight to 50% by weight of the coating material.

27. The particle of claim 25, comprising from 10% by weight to 25% by weight of the coating material.

28. The particle of claim 24, wherein R¹, R²and R³are identical.

29. The particle of claim 28, wherein R¹, R²and R³are methyl groups.

30. The particle of claim 24, wherein among R¹, R²and R³, at least 1 or 2 are methyl groups, and the other or others have two or more carbon atoms.

31. The particle of claim 24, wherein the anion X⁻ is selected from the group consisting of chloride, fluoride, iodide, bromide, nitrate, hydroxide, phosphate, hydrogen phosphate, dihydrogen phosphate, pyrophosphate, metaphosphate, hexafluorophosphate, carbonate, hydrogen carbonate, sulfate, hydrogen sulfate, C_{1 20}-alkyl sulfate, C_1-20-alkylsulfonate, optionally C_1-18-alkyl-substituted arylsulfonate, chlorate, perchlorate, acetate, laurate, benzoate, citrate, formate, and mixtures thereof.

32. The particle of claim 24, wherein the anion X⁻ is selected from the group consisting of halides, anions of C_1-24-carboxylic acids, and mixtures thereof.