Patentamt JEuropaisches3 European Patent Office ® Publication number: 0 1 74 1 32 Office europeen des brevets B1 ® EUROPEAN PATENT SPECIFICATION C 11 D 11/02 ® Date of publication of patent specification: 14.12.88 © Int. CI.4: C 11 D 3/39, (2?) Application number: 85305933.5 ® Date of filing: 21.08.85 ® Bleach activator compositions manufacture and use thereof in laundry compositions. (§) Priority: 01.09.84 GB 8422158 (73) Proprietor: THE PROCTER & GAMBLE COMPANY One Procter & Gamble Plaza (43) Date of publication of application: Cincinnati Ohio 45202 (US) 12.03.86 Bulletin 86/11 (§) BECH ® Proprietor: Procter & Gamble Limited Hedley House Publication of the grant of the patent: Gosforth Newcastle upon Tyne NE99 1EE (GB) 14.12.88 Bulletin 88/50 (§) GB ® Designated Contracting States: (72) Inventor: Divo, Michael AT BE CH DE FR GB IT LI IML Dr. Schoenenbornstrasse 22 D-5350 Euskirchen (DE) (§) References cited: EP-A-0 070 474 (7J) Representative: Brooks, Maxim Courtney et al EP-A-0106 634 Procter & Gamble (NTC) Limited Whitley Road FR-A-2148203 Longbenton FR-A-2307 869 Newcastle-upon-Tyne NE129TS (GB) 03 GB-A-2 015 050 CM CO Note: Within nine months from the publication of the mention ot the grant ot tne turopean paxeni, any per&un may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall CL be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been UJ paid. (Art. 99(1 ) European patent convention). Courier Press, Leamington Spa, England. EP 0 174 132 B1 Description The present invention relates to bleach activator compositions. More particularly, it relates to bleach activator compositions prepared by spray drying for use in or with a detergent and/or bleach composition. 5 The bleach activator compositions have excellent storage stability, physical strength and water- dispersibility, as well as simplified processing and reduced segregation in a full detergent or bleach product. The invention also relates to a process of making the compositions and also to laundry compositions containing water-soluble bleach activators. It is well known that peroxygen bleaching agents, e.g., perborates, percarbonates, perphosphates and w persilicates, are highly useful for chemical bleaching of stains found on both colored and white fabrics. Such bleaching agents are most effective at high wash solution temperatures, i.e., about 60°C to 70°C. In recent years, attempts have been made to provide bleaching compositions that are effective at lower wash solution temperatures. In consequence, there has been much industrial research to develop substances generally referred to as bleach activators, that render peroxygen bleaches effective at bleach solution 15 temperatures below 60°C. These low temperature bleaches are useful in a variety of products intended for use under machine or hand-wash conditions, e.g., additive, pre-additive or soak-type laundry compositions as well as all-purpose detergent compositions. A bleach activator can generally be described as an organic peroxy acid bleach precursor which in the bleaching solution reacts with an inorganic peroxygen bleaching agent with release of the organic peroxy 20 acid. Many such bleach activators are known in the art, most of which contain perhydrolysable N-acyl or 0- aryl residues. Examples of these include succinic, benzoic and phthalic anhydrides, tetracetylethylene diamine and tetracetylglycoluril, all of which are water-insoluble materials to varying degrees. See FR — A — 2,148,203 for a description of such materials. Water-soluble bleach activators are also known in the art and are described in detail in, for example, 25 US— A— 4,412,934 and EP— A— 0120591. These activators have a number of advantages over water- insoluble materials including rapid dispersibility in wash or bleach solution and also the ability to exhibit surface bleaching. On the downside, however, water-solubility greatly exacerbates activator stability problems resulting from interaction with moisture and peroxygen bleaching agent during prolonged storage in the bleach or detergent composition. 30 It is also known in the art to incorporate bleach activators in a detergent slurry for spray-drying (see GB — A — 1 540832 and FR — A — 2307869) whereby the resulting detergent composition comprises the bleach activator homogeneously distributed therein. EP— A— 0070474 also relates to the spray drying of bleach activators. In the case of water-soluble bleach activators, however, it is found that the conventional crutching and spray-drying process results in essentially complete degradation of the activator. 35 It has now been found, however, that water-soluble bleach activators can be successfully crutched and spray-dried by incorporating an inorganic hydratable material in the crutcher slurry mix and adjusting the pH of the slurry to within the range from 3 to 8 prior to spray-drying. Moreover, the subsequent granule is found to combine excellent stability characteristics when stored in a detergent or bleach composition, as well as improved dispersibility on addition to the wash or bleach solution. 40 According to the present invention, therefore, there is provided a bleach activator composition in the form of spray-dried granules having an inner core comprising organic peroxyacid bleach precursor and a surface coating comprising a water-soluble or water-dispersible, inorganic hydratable material, characterised in that the organic peroxy acid bleach precursor is water-soluble and wherein the composition has a pH (1% aqueous solution) in the range from 3 to 8. 45 The invention also relates to a process of making a granular bleach activator composition comprising forming an aqueous slurry of a water-soluble organic peroxyacid bleach precursor and a water-soluble or water-dispersable inorganic hydratable material, adjusting the pH of the slurry (1% solids) to within the range from 3 to 8, preferably from 3.5 to 7 and subjecting the slurry to spray-drying. In its composition aspect, the compositions of the invention take the form of granules having an inner so core comprising water-soluble bleach precursor encapsulated or substantially enclosed within a coating of water-soluble or dispersible inorganic hydratable material. In preferred embodiments, the inner core exists as an essentially spherical droplet or aggregation of spherical droplets of the bleach precursor. The outer coating on the other hand comprises a water-soluble or water-dispersible inorganic hydratable material which in preferred embodiments, consists majorly (at least 50%, preferably at least 55 75%) of one or more acid salts having a pKa in the range from 1 to 9, preferably from 2 to 7, more preferably from 3 to 6.5. Suitable inorganic hydratable materials include disodium dihydrogen pyrophosphate, tetrasodium monohydrogen tripolyphosphate, trisodium dihydrogen tripolyphosphate, sodium bicarbonate, acidified pentasodium tripolyphosphate, acidified borax and acidified aluminosilicates and mixtures thereof. Strong acid hydratable salts such as sodium sulphate and magnesium sulphate can also 60 be incorporated in minor amounts. In the final spray-dried granule, the hydratable material is preferably hydrated to an extent of from 10% to 90%, preferably from 30% to 60% of its hydration capacity (based on the highest hydrate which is stable at room temperature). Preferably, the inorganic hydratableTnaterial has no hydrate transition point below 40°C or consists majorly of such material (greater than 50%, preferably greater than 75% of total inorganic hydratable material). 65 In the present invention, pH control is all-important both for successful spray drying of the aqueous 2 P 0 174 132 Bl slurry mix and for stability ot the resulting granular composition, in particular, me (jiuvisium ui a un- regulated outer coating based on pa rtly-hyd rated inorganic hydratable material appears to be especially beneficial in providing both physical and chemical stabilization of the water-soluble bleach activator in the final detergent or bleach product. In the practice of the invention the pH of the granular composition (1% 5 solution) should lie within the range from 3 to 8, preferably from 3.5 to 7, more preferably from 4 aqueous % to 6.5, while the aqueous slurry for spray-drying should also be adjusted to within the same pH range (1 solids solution). Adjustment of pH can be achieved in various ways, for example, by incorporating inorganic acid salts having the required pH characteristics, or by adding mineral acids or organic acids to the crutcher mix to lower the pH into the prescribed range. Suitable organic acids herein include C8— C24 '0 fatty acids, polycarboxylic acids, aminopolycarboxylic acids, polyphosphonic acids, aminopolyphosphonic acids and mixtures thereof. The spray-dried granular bleach activator compositions herein generally comprise from 0.1% to 50%, preferably from 1 % to 45% bleach precursor, and from 10% to 99.9%, preferably from 25% to 90%, more preferably from 35% to 90% alkaline inorganic hydratable material. In addition, they generally have a bulk <5 density of from 300 to 900 grams/litre, preferably from 450 to 750 grams/litre, and a weight average particle size of from 0.15 to 3 mm, preferably from 0.5 mm to 1.4 mm. 0.05% The aqueous slurry for spray drying comprises generally from 30% to 60% water, from to 35%, preferably from 0.5% to 30%, more preferably from 2% to 25% bleach precursor, and from 10% to 69.95%, preferably from 14% to 63% alkaline inorganic hydratable material. The slurry is then heated to a ;o temperature of from 60°C to 90°C and spray-dried in a current of air having an inlet temperature of from 250°Cto350°C, preferably from 275°Cto 330°C, and an outlet temperature of from 95°Cto 125°C, preferably from 100°C to 115°C. The bleach activators used in the compositions and process of the invention are water-soluble materials, being soluble generally to an extent of at least 1 %, preferably at least 5% by weight at 25°C and ?5 pH 7.