Europaisches Patentamt (19) European Patent Office Office europeenpeen des brevets EP 0 520 582 B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publication and mention (51) lntCI.6: C11D 11/02, C11D 3/12, of the grant of the patent: C11D 17/06, C11D 3/20 04.02.1998 Bulletin 1998/06 (21) Application number: 92201881.7 (22) Date of filing: 24.06.1992 (54) Process for preparing zeolite based spray-dried detergent compositions Verfahren zur Herstellung von spruhgetrockneten Waschmittelzusammensetzungen auf Zeolithbasis Procede de preparation de compositions detergentes sechees par pulverisation a base de zeolithe (84) Designated Contracting States: • Kolodziej, Richard M. AT BE CH DE DK ES FR GB IT LI LU NL SE Highland Park, New Jersey (US) (30) Priority: 28.06.1991 US 723146 (74) Representative: Smulders, Theodorus A.H.J., Ir. et al (43) Date of publication of application: Vereenigde Octrooibureaux 30.12.1992 Bulletin 1992/53 Nieuwe Parklaan 97 2587 BN 's-Gravenhage (NL) (73) Proprietor: Colgate-Palmolive Company New York, N.Y. 10022-7499 (US) (56) References cited: EP-A- 0 001 853 EP-A- 0 191 187 (72) Inventors: EP-A- 0 191 187 EP-A- 0 313 144 • Cush, James Frank, Jr. EP-A- 0 319 053 EP-A- 0 344 629 Washington Township, New Jersey (US) DO CM 00 CM LO Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice the Patent Office of the Notice of shall be filed in o to European opposition to European patent granted. opposition a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. a. 99(1) European Patent Convention). LU Printed by Jouve, 75001 PARIS (FR) EP 0 520 582 B1 Description BACKGROUND OF THE INVENTION 5 The present invention relates to a process for manufacturing a free-flowing spray-dried particulate detergent com- position containing a zeolite builder and at least one surface active detergent compound, which composition is char- acterized by improved particle strength and integrity concomitant with reduced residue deposition properties. More particularly, this invention relates to a process for producing a spray-dried detergent composition characterized by the absence of sodium silicate in the aqueous crutcher slurry and the presence of a bead strengthening agent to provide 10 particles having desired properties of enhanced mechanical strength. The invention also relates to particulate detergent compositions produced by the aforementioned process of manufacture which have improved washing properties by virtue of providing little, if any, residue on washed fabrics as well as having excellent mechanical strength and resistance to breakage so as to allow such compositions to be extensively stored, handled and transported without causing undo abrasion or fragmentation of the particles. is Commercial detergent compositions containing water softening aluminum silicate builders, such as zeolites, have long been marketed in the United States and Europe. Recently, zeolites in commercial laundry detergent compositions have become especially prevalent due, primarily, to increased governmental concern with phosphates in sewage ef- fluents. This concern has been manifested by legislation aimed at curbing the use of phosphates in detergent compo- sitions because of their attributed nutritive effect in enhancing algae growth in inland waters, presumably at the expense 20 of other forms of aquatic life. Consequently, recent years have been marked by an increased emphasis on providing low phosphate or phosphate-free commercial detergent compositions, commonly referred to as low P or zero P (or No-P) detergent products. Zeolites, natural as well as synthetic, are known to be effective calcium sequestrants and are commonly used to replace phosphates, such as sodium tripolyphosphate, as detergent builders in commercial low-P or zero-P detergent 25 compositions. But the presence of zeolite has heretofore often created a problem with regard to water-insoluble residue being deposited on laundry washed with such zeolite-containing compositions. This is generally attributed to its inter- action with sodium silicate, a common ingredient in spray-dried particulate compositions, to form an insoluble zeolite- silicate agglomerate which becomes entrapped in the washed fabrics and forms an unsightly "residue" on the laundered clothing, seriously detracting from the washing performance. 30 Sodium silicate is generally considered a critical ingredient in particulate detergent compositions. It is reported to serve many functions: first, as a corrosion inhibitor to provide protection for metal parts of the washing machine which come into contact with aqueous solutions of the washing composition; second, to increase the alkalinity of the aqueous washing solution; and most important, particularly in a spray-dried composition, it serves to provide stability and integrity to the detergent particles or beads formed during the spray-drying operation. 35 It has now been discovered that the problem of residue deposition can be substantially avoided while maintaining bead stability and integrity in a spray-dried composition by eliminating sodium silicate from the detergent composition, substantially reducing the presence of surfactants in the crutcher slurry and incorporating into the crutcher slurry a bead strengthening agent as hereinafter described, such as sodium citrate. Spray-dried detergent compositions containing a zeolite builder and sodium citrate are well known in the detergent 40 art. U.S. Patent 3,801 ,511 to Lemoff discloses a spray-dried detergent composition in which an anti-caking agent such as sodium citrate is added to the aqueous slurry prior to spray-drying so as to provide crisp, free-flowing granules of said detergent composition. Sodium silicate is a preferred component of the detergent composition. U.S. 4,303,556 to Llenado describes a spray-dried detergent composition containing an aluminosilicate ion ex- change material, sodium silicate and optionally an auxiliary builder which may be citric acid. Anionic surfactants are 45 added to the aqueous slurry which is spray dried. U.S. 4,861 ,503 to Hollingsworth discloses a low-phosphate spray- dried detergent composition prepared from a crutcher slurry containing one or more anionic or nonionic detergent active compounds; from 0 to 10% of sodium silicate; a non-phosphate builder; from 0.5 to 2.5% of a salt of succinic acid; and 0.5 to 10% of a polymeric polycarboxylate. The compositions described in the Examples contain 4 or 5% sodium silicate. so U.S. Patent 5,024,778 to Grecsek describes zeolite-containing spray dried base beads for detergent compositions which contain 5 to 60% of zeolite, 0 to 5% of water soluble silicate, 2 to 40% of bentonite and about 5 to 60% of polyphosphate. The presence of bentonite is intended to prevent the interaction of zeolite and silicate to form an ob- jectionable aggregate which deposits on washed fabrics. The patent also discloses using citric acid and magnesium sulfate as anti-gelling processing aids to be added to the crutcher mix when the crutcher includes silicate in combination 55 with carbonate and/or bicarbonate because of the tendency of such combination to solidify or cause gelation in the crutcher. U.S. Patent 4,231 ,887 to Denney discloses zeolite agglomerates for detergent compositions in a matrix of sodium citrate and ethoxylated linear alcohol. The sodium citrate is referred to as a "crisping agent" which imparts crispness 2 EP 0 520 582 B1 to the agglomerates while permitting them to disintegrate upon contact with water. In EP 1853 naming Smith and Maxwell as inventors there is disclosed a zeolite-containing detergent composition which also contains sodium citrate. The working Examples 1-6 at page 26 of the publication describe spray dried compositions containing a minimum of 10%, by weight, of anionic and/or nonionic detergent compounds. In some of these compositions sodium citrate and 5 zeolite are present in the finished composition in the absence of sodium silicate. The surfactant detergent compounds are all added to the crutcher slurry; none being post-added or applied subsequent to spray drying to the spray-dried particles. U. S. Patent 4,988,454 to Eertink et al describes a process for preparing a low or zero-phosphorous detergent powder containing zeolite, sodium silicate, surfactant and polyacrylate. The process of manufacture restricts the 10 amount of silicate in the crutcher slurry to no more than 2%, by weight, of the silicate in the final powder, and compen- sates for such restricted amount of silicate by post-dosing sodium silicate with the spray-dried powder as well as incorporating a polymer or copolymer of acrylic acid as a "structuring agent". SUMMARY OF THE INVENTION 15 The present invention provides a process for producing a free-flowing spray-dried particulate detergent composition having a density of from 0.3 to 1.0 g/cc and containing a zeolite and one or more anionic, nonionic and/or cationic surface active detergent compounds, said detergent composition having improved particle mechanical strength and integrity to allow extensive storage and handling of the composition with only minimum breakage and abrasion of the 20 particles concomitant with high solubility characteristics such that the amount of visible residue deposited on fabrics laundered with such detergent composition is significantly minimized comprising the steps of: (a) forming an aqueous crutcher slurry containing (i)