PROCESS FOR PREPARING GRANULAR DETERGENT COMPOSITIONS

Abstract: A process for preparing a granular detergent composition with improved wash-delivery properties comprises a first step of preparing a liquid component containing an anionic surfactant, a nonionic surfactant and a structurant and a second step comprising admixture of the liquid component with a solid component in a granulator. An optional third step comprises drying and/or cooling. The structurant is incorporated in an amount such that the liquid component is pumpable at temperatures of 50 DEG C or more but causes sufficient solidification to form a free-flowing granulated product. In bleach-containing products, the process also provides for reduced fabric dye damage in the wash.

Description: 1 - PROCESS FOR PREPARING GRANULAR DETERGENT COMPOSITIONS FIELD OF THE INVENTION The present invention relates to the preparation of a granular detergent composition or component containing anionic and nonionic surfactants, by mixing and granulating liquid and solid components, preferably continuously. The invention is especially applicable to the production of granular compositions containing zeolite as a builder. BACKGROUND OF THE INVENTION The production of detergent powders by spray-drying is long known in the art, with spray-dried products generally providing good powder delivery characteristics such as dispensing and dissolution. However, the spray-drying process is both capital and energy intensive and as a result the product is expensive. Consequently, the detergent industry has looked for methods of producing powders which are more cost effective and which produce powders of higher bulk density than that ordinarily achievable through spray drying . In recent years, there has been much interest in the production of detergent products by processes which employ mainly mixing, without the use of spray-drying. In this type of process, the various components are dry-mixed and optionally granulated with a liquid binder. Liquid binders typically used in such granulation processes are nonionic surfactants, anionic surfactants, acid precursors of anionic surfactants or any mixture thereof. Using these granulation - 2 - processes, detergent powders having a high bulk density, typically 700 to 900 g/1, have been produced. A problem encountered with high bulk density, concentrated powders is slow and/or incomplete dissolution in the wash liquor, leading to undissolved product residues, generally white in colour, on the laundry fabric. For example, zeolite-containing concentrated powders are known to have a problem with undissolved zeolite-containing powder getting trapped in the cloth fibre; this manifests itself as white specks, clearly visible and displeasing to the eye . In addition to the undesirability of undissolved residues on the fabric, undissolved bleach-containing powder trapped in the cloth fibre can lead to fabric colour damage, generally known as spot damage. We have found that in the case of detergent compositions containing both anionic and nonionic surfactants, prepared by mixing liquid components with solid particulate components in a mixer/granulator, the level of residues and fabric colour damage in the wash can be significantly reduced by premixing the anionic and nonionic surfactants to form a structured blend prior to the granulation process . PRIOR ART EP 420 317 (Unilever) discloses a process for the continuous preparation of granular detergent compositions or components having a higher density than is achievable in spray-drying processes. The process consists of three steps, an agglomeration in a high-speed mixer, a densification in a moderate-speed granulator densifier whereby the material is brought or maintained in a deformable state, and the drying 3 - and/or cooling of the product (e.g. in a fluid bed) . The liquid binder in the agglomeration step is a liquid acid precursor of an anionic surfactant, which is neutralized in situ by a solid water-soluble alkaline inorganic material (e.g. sodium carbonate) in the high-speed mixer. EP 544 365 (Unilever) discloses a process for the preparation of a high active alkyl sulphate granular composition in the same equipment described in EP 420 317 or alternatively in a batch granulation. In this case a mixture of a sodium or potassium salt of an alkyl sulphate, e.g. a primary alkyl sulphate (PAS) , and an alkoxylated nonionic surfactant is used as the liquid phase for the granulation in the high speed mixer. In order to obtain product with good powder properties, the viscosity of the liquid phase may be increased by adding one or more components, such as, for example, water and soap. The increased viscosity appeared to give more control over the agglomeration process . EP 265 203 (Unilever) discloses liquid surfactant compositions mobile at 20-80°C which contain a sodium or potassium salt of an alkylbenzene sulphonate or alkyl sulphate, an ethoxylated nonionic surfactant and water, the amount of water not exceeding 10% by weight. Such liquid surfactant compositions may be sprayed onto a solid particulate absorbent material, for instance a porous spray- dried base powder having a low bulk density and containing little or no actives, to form a detergent base powder having an increased bulk density. - 4 - EP 436 240 (Unilever) discloses liquid surfactant compositions mobile at a temperature within the range 20-80°C consisting essentially of those components described in EP 265 203 and in addition a fatty acid. The liquid surfactant compositions are sprayed onto phosphate-free solid particulate absorbent materials, such as spray-dried zeolite or layered silicates, to produce detergent compositions having bulk densities of at least 500 g/1 and having improved dispensing properties. There is no teaching of agglomeration of the solid material in a mixer/granulator, merely absorption of the liquid surfactant into the solid material in a rolling drum apparatus. EP 507 402 (Unilever) describes a process for preparing a liquid surfactant composition comprising anionic surfactant, nonionic surfactant and having a relatively low water content, wherein essentially equimolar amounts of neutralising agent and liquid acid precursor of the anionic surfactant are blended simultaneously with the nonionic surfactant. It is especially preferred that the process be carried out continuously in a loop reactor. The liquid surfactant compositions may additionally contain a fatty acid, and may be applied in a process for making high bulk density granular detergent compositions having a high active detergent level, as disclosed by EP 367 339 (Unilever) . Unpublished International Patent Application No. PCT/EP97/04749 (which has a priority date of 10/09/96) describes a process providing improved granularity for powders produced by a mixing process and containing sodium tripolyphosphate (STP) or other solids having a low-liquid carrying capacity and/or hydratable properties. The process - 5 of PCT/EP97/ 04749 also provides extra benefits for builders such as zeolites, enabling the manufacture of granular products with a lower relative humidity without drying than previously available. These low humidity levels allow percarbonate bleaches to be post-dosed, these being preferred over perborates on environmental grounds . According to the process described in PCT/EP97/04749 , a liquid component of the detergent is formulated with a structurant so as to remain pumpable at the temperature at which the liquid component is formed and then admixing it with a solid component at a lower temperature at which the structurant causes solidification of the mixture. There is no disclosure in PCT/EP97/04749 of the dissolution properties of the powders produced by the claimed process, or of the residue levels or bleach damage in the wash. SUMMARY OF THE INVENTION We have surprisingly found that powders produced following the process claimed in PCT/EP97/04749 have, in addition to good granularity, much improved wash-delivery properties. Thus according to a first aspect, the present invention provides for the use of a process for preparing a granular detergent composition with improved wash-delivery properties, the process comprising the steps of: (i) preparing a liquid component comprising an anionic surfactant or precursor thereof, a nonionic surfactant and a structurant; (ii) admixing the liquid component with a solid component in a high speed mixer/granulator; and optionally (iii) drying and/or cooling, the structurant being incorporated in an amount such that the liquid component is pumpable at temperatures of 50 2 C or more (e.g. 60°C or more) but causes sufficient solidification during the second and/or third steps to form a free-flowing granulated product . Granular detergent compositions according to the invention may be in the form of complete products ready for sale to the consumer. Alternatively, they may be formulated as base powders or adjuncts for admixture with other ingredients, such as, for example, a bleaching system, to form final detergent products . Accordingly, in a second aspect, the present invention provides for the use of a process in the preparation of a bleach-containing detergent product, the detergent product producing less dye damage in the wash, the process comprising the steps defined in the first aspect. The invention is particularly applicable to powders containing zeolite as a builder. However, it also applies to powders containing other builder materials such as, for example, STP, citrates and carbonates. In a third aspect, the invention provides a granular detergent composition or component with improved dissolution properties obtainable by the process defined in the first aspect, said granular detergent composition comprising an - 7 anionic surfactant, an nonionic surfactant, soap and a crystalline and/or amorphous aluminosilicate as a detergency builder. The present invention is particularly applicable to powders containing an alkylbenzene sulphonate as the anionic surfactant . In a fourth aspect, the present invention provides a process for preparing a granular detergent composition, the process comprising the steps of : (i) preparing a liquid component comprising surfactant and a structurant, the structurant being incorporated in an amount such that the liquid component is pumpable at temperatures of 50 2 C or more but causes sufficient solidification during the second and/or third steps to form a free- flowing granulated product; (ii) admixing the liquid component with a solid component in a high speed mixer/granulator; and optionally (iii) drying and/or cooling, wherein the surfactant comprises an anionic surfactant or precursor thereof and a nonionic surfactant, the solid component comprises an aluminosilicate and whereby the granular detergent composition has a disintegration rate of _ι greater than 25 μms DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Delivery to the wash may be assessed may measuring particular properties inherent in the detergent powder as - 8 - are well-known to the person skilled in the art. These include, for example, solubility, dissolution and disintegration, which can all be measured by well-known methods reported in the literature. Solubility, for example, can be measured in an "insolubles" test. In a typical insolubles test, a sample of the powder (e.g. lOg) is stirred in water (e.g. 500 ml) for 2 minutes at a relevant temperature. The mixture is then filtered through a sieve and any powder residues dried and weighed. Disintegration rate is another parameter by which delivery to the wash may be evaluated. The process of disintegration involves both the break up of particulate material into smaller pieces as well as dissolution of the particulate material into solution. The disintegration rate of the powder particles in the present invention is measured using a laser diffraction technique. For example, around 30 particles of a particular size range (e.g. between 500 and 710 μm) are placed in a cuvet filled with a 0.1 w/w% carbonate solution. The laser then records the average powder particle size during disintegration. The disintegration rate is then taken to be the average rate of decrease in average particle diameter from the start of the measurement until the particles have dissolved to less than 50 μm in diameter. The granular detergent compositions of the invention typically have a disintegration rate of -1 -1 greater than 25 μms , preferably greater than 50 μms , more _1 preferably greater than 75 μms - 9 - In contrast to measuring properties inherent in the powders added to the wash, the actual results of the wash can be evaluated in assessing the delivery properties of the powder. For example, the level of powder residues on the washed fabrics can be measured. The granular product so prepared can be considered to be free flowing if it has a dynamic flow rate (DFR) of more than 90 mis "1 . Conveniently, DFR can be measured by a technique whereby known volume of powder is permitted to flow through a calibrated orifice and tube. The flow time between two light sensors is automatically recorded and the DFR is calculated with the known volume and the recorded flow time. Granular detergent compositions according to the invention may have a bulk density of 550 g/1, more preferably at least 650 g/1. However, these products may also be produced with lower bulk densities. The resultant granulated products of the invention when tabletted, produce tablets having a high degree of hardness as measured by break strength (P max ) and E modulus (E moc j) - Preferred embodiments of process and compositions according to the present invention may be characterised by the strength and E-modulus of a sample of (a) tabletted composition produced by the process; and/or (b) tablet formed by cooling of the liquid component until it solidifies. 10 - The strength (hardness) measurement can be obtained using an Instron pressure apparatus. The powder is tabletted in a punch and die to form a tablet 9 mm in diameter and 16 mm in height, formed by exerting a maximum pressure of 10 tons on the tablet surface. In the case of a solidified liquid component taken from the process before it contacts the solid component, the tablet diameter is 14 mm and its height is 19 mm. The tablet (powder or liquid component) is destroyed between a fixed and a moving plate . The speed of the moving plate is set to 5 mm/min, which causes a measuring time of about 2 sec. The pressure curve is logged on a computer. Thus, the maximum pressure (at the moment of tablet breaking) is given and the E-modulus is calculated from the slope. For the granular product, the minimum value of P ma χ is preferably 0.5 M Pa, most preferably 2 M Pa and the minimum value of E moc j is preferably 20 M Pa, most preferably 50 M Pa. However, for the solidified liquid component, P max at 20°C is preferably a minimum of 0.2 M Pa, e.g. from 0.3 to 0.5 M Pa. At 55°C, a typical range is from 0.05 to 0.25 M Pa . At 20 a C, E mo a for the liquid blend is preferably a minimum of 3 M Pa, e.g. from 5 to 10 M Pa. The liquid component is preferably prepared in a shear dynamic mixer for premixing the components thereof and performing any neutralisation of anionic acid precursor. The dynamic mixer is preferably located in a loop with a heat exchange to remove the heat of reaction of such neutralisation . - 11 In the context of the present invention, the term "structurant" means any component which enables the liquid component to achieve solidification in the granulator and hence good granulation, even if the solid component has a low liquid carrying capacity. Structurants may be categorised as those believed to exert their structuring (solidifying) effect by one of the following mechanisms, namely: recrystallisation (e.g. silicate or phosphates) ; creation of a network of finely divided solid particles (e.g. silicas or clays); and those which exert steric effects at the molecular level (e.g. soaps or polymers) such as those types commonly used as detergency builders. One or more structurants may be used. Soaps represent one preferred class of structurant, especially when the liquid component comprises a liquid nonionic surfactant. In many cases it may be desirable for the soap to have an average chain length greater than the average chain length of the liquid nonionic surfactant but less than twice the average chain length of the latter. If desired, solid components may be dissolved or dispersed in the liquid component. Typical amounts of ingredients in the essential liquid component as % by weight of the liquid component are as follows: preferably from 10% to 98% by weight of nonionic surfactant, more preferably from 30% to 70% by weight, and especially from 40% to 50% by weight; - 12 - preferably from 98% to 10 by weight of anionic surfactant, more preferably from 70% to 30%, and especially from 50% to 40% by weight; preferably from 2% to 30% by weight of structurant, more preferably from 5% to 20%, yet more preferably from 5% to 15% by weight, and especially from 10% to 15% by weight. In addition to the anionic surfactant or precursor thereof, nonionic surfactant and structurant, the liquid component also contain other organic solvents. The liquid component is also preferably substantially non- aqueous. That is to say, the total amount of water therein is not more than 15% by weight of the liquid component, preferably not more than 10% by weight, typically from 5% to 8%, especially from 6% to 7%. Typically, from 3% to 4% by weight of the liquid component may be water as the reaction by-product and the rest of the water present will be the solvent in which the alkaline material was dissolved. The liquid component is very preferably devoid of all water other than that from the latter-mentioned sources, except perhaps for trace amounts/impurities . It is very much preferred to form some or all of any anionic surfactant in situ in the liquid component by reaction of an appropriate acid precursor and an alkaline material such as an alkali metal hydroxide, e.g. NaOH. Since the latter normally must be dosed as an aqueous solution, that 13 - inevitably incorporates some water. Moreover, the reaction of an alkali metal hydroxide and acid precursor also yields some water as a by-product . However, in principle, any alkaline inorganic material can be used for the neutralisation but water-soluble alkaline inorganic materials are preferred. Another preferred material is sodium carbonate, alone or in combination with one or more other water-soluble inorganic materials, for example, sodium bicarbonate or silicate. As alluded to above, sodium carbonate can provide the necessary alkalinity for the wash process, but it can additionally serve as a detergency builder. In this case the invention may be advantageously used for the preparation of detergent powders in which sodium carbonate is the sole or principal builder. Then, substantially more carbonate will be present than required for the neutralisation reaction with the acid anionic surfactant precursor. The liquid component may optionally comprise dissolved solids and/or finely divided solids which are dispersed therein. The only limitation is that with or without dissolved or dispersed solids, the liquid component should be pumpable at temperatures of 50°C or greater or at any rate, 60°C or greater e.g. 75°C. Preferably it is solid at below 50°C, preferably at 25°C or less. A definition of solid can be found in the Handbook of Chemistry and Physics, CRC Press, Boca Raton, Florida, 67th edition, 1986. Generally speaking, pumpable liquid components have a viscosity no greater than 1 Pas at the shear rate of the 14 - pumping. Typically, the shear rate of the pumping will be - 1 greater than 1 s The structurants cause solidification in the liquid component preferably to produce blend and tablet strength as described hereinbefore. Typically, the temperature in the granulation is more than 10 e C, preferably more than 20°C below the temperature at which the blend is prepared and pumped into the granulator. If the solid component comprises or substantially consists of an aluminosilicate builder, the weight ratio of liquid component to the solid component when the two are brought into contact for mixing is preferably from 0.4:1 to 0.7:1. If the solid component comprises or substantially consists of a phosphate builder, this ratio is preferably from 0.25:1 to 0.5:1. Suitable anionic surfactants are well-known to those skilled in the art. Examples suitable for incorporation in the liquid phase include alkylbenzene sulphonates, particularly linear alkylbenzene sulphonates having an alkyl chain length of C 8 -C 5 ; primary and secondary alkyl sulphates, particularly C1 2 -C1 5 primary alkyl sulphates; alkyl ether sulphates; olefin sulphonates; alkyl xylene sulphonates; dialkyl sulphosuccinates; and fatty acid ester sulphonates. Sodium salts are generally preferred. The nonionic surfactant component of the liquid phase may be any one or more liquid nonionics selected from primary and secondary alcohol ethoxylates, especially C 8 -C 20 aliphatic 15 - alcohols ethoxylated with an average of from 1 to 20 moles ethylene oxide per mole of alcohol, and more especially the Cιo~Ci 5 primary and secondary aliphatic alcohols ethoxylated with an average of from 1 to 10 moles of ethylene oxide per mole of alcohol . Non-ethoxylated nonionic surfactants include alkylpolyglycosides, glycerol monoethers, and polyhydroxyamides (glucamide) . The liquid acid precursor may be selected from linear alkyl benzene sulphonic (LAS) acids, alphaolefin sulphonic acids, internal olefin sulphonic acids, fatty acid ester sulphonic acids and combinations thereof. The process of the invention is especially useful for producing compositions comprising alkyl benzene sulphonates by reaction of the corresponding alkyl benzene sulphonic acid, for instance Dobanoic acid ex Shell . Linear or branched primary alkyl sulphates (PAS) having 10 to 15 carbon atoms can also be used. The solid component with which the liquid phase is admixed preferably comprises a detergency builder. The total amount of detergency builder in the final compositions is suitably from 10 to 80 wt%, preferably from 15 to 60 wt% . The builder may be present in an adjunct with other components or, if desired, separate builder particles containing one or more builder materials may be employed. The present invention is especially applicable to use where the solid component comprises builders selected from crystalline and amorphous aluminosilicates, for example zeolites as disclosed in GB-A-1 473 201; amorphous aluminosilicates as disclosed in GB-A-1 473 202; and mixed 16 crystalline/amorphous aluminosilicates as disclosed in GB 1 470 250; and layered silicates as disclosed in EP-B-164 514. Aluminosilicates, may suitably be present in a total amount of from 10 to 60 wt% and preferably an amount of from 15 to 50 wt% . The zeolite used in most commercial particulate detergent compositions is zeolite A. Advantageously, however, maximum aluminium zeolite P (zeolite MAP) described and claimed in EP-A-384 070 may be used. Zeolite MAP is an alkali metal aluminosilicated of the P type having a silicone to aluminium ratio not exceeding 1.33, preferably not exceeding 1.15, and more preferably not exceeding 1.07. Other suitable builders include hydratable salts, preferably in substantial amounts such as at least 25% by weight of the solid component, preferably at least 10% by weight. Hydratable solids include inorganic sulphates and carbonates, as well as inorganic phosphate builders, for example, sodium orthophosphate, pyrophosphate and tripolyphosphate. Other inorganic builders that may be present include sodium carbonate (as mentioned above, an example of a hydratable solid) , if desired in combination with a crystallisation seed for calcium carbonate as disclosed in GB-A-1 437 950. As mentioned above, such sodium carbonate may be the residue of an inorganic alkaline neutralising agent used to form a nonionic structurant iτι situ. Organic builders that may be present include polycarboxylate polymers such as polyacrylates, acrylic/maleic copolymers, and acrylic phosphinates ; monomeric polycarboxylates such as 17 - citrates, gluconates, oxydisuccinates, glycerol mono-, di- and trisuccinates, carboxymethyloxysuccinates, carboxymethyloxymalonates , dipicolinates , hydroxyethyliminodiacetates, aminopolycarboxylates such as nitrilotriacetates (NTA) , ethylenediaminetetraacetate (EDTA) and iminodiacetates, alkyl- and alkenylmalonates and succinates; and sulphonated fatty acid salts. A copolymer of maleic acid, acrylic acid and vinyl acetate is especially preferred as it is biodegradable and thus environmentally desirable. This list is not intended to be exhaustive. Especially preferred organic builders are citrates, suitably used in amounts of from 5 to 30 wt%, preferably from 10 to 25 wt%; and acrylic polymers, more especially acrylic/maleic copolymers, suitably used in amounts of from 0.5 to 15 wt%, preferably from 1 to 10 wt% . The builder is preferably present in alkali metal salt, especially sodium salt, form. Granular detergent compositions of the invention may contain, in addition to the nonionic and anionic surfactants of the liquid component, one or more other detergent-active compounds (surfactants) which may be chosen from soap and non-soap anionic, cationic, nonionic, amphoteric and zwitterionic detergent-active compounds, and mixtures thereof. These may be dosed at any appropriate stage before or during the process. Many suitable detergent-active compounds are available and are fully described in the literature, for example, in "Surface-Active Agents and Detergents", Volumes I and II, by Schwartz, Perry and Berch. The preferred detergent-active compounds that can be used are soaps and synthetic non-soap anionic and nonionic compounds . 18 Detergent compositions according to the invention may also contain a bleach system, desirably a peroxy bleach compound, for example, an inorganic persalt or organic peroxyacid, capable of yielding hydrogen peroxide in aqueous solution. The peroxy bleach compound may be used in conjunction with a bleach activator (bleach precursor) to improve bleaching action at low wash temperatures. An especially preferred bleach system comprises a peroxy bleach compound (preferably sodium percarbonate optionally together with a bleach activator) , and a transition metal bleach catalyst as described and claimed in EP-A-458 397 and EP-A-509 787. Usually, any bleach and other sensitive ingredients, such as enzymes and perfumes, will be post-dosed after granulation along with other minor ingredients. Typical minor ingredients include sodium silicate; corrosion inhibitors including silicates; antiredeposition agents such as cellulosic polymers; fluorescers; inorganic salts such as sodium sulphate, lather control agents or lather boosters as appropriate; proteolytic and lipolytic enzymes; dyes; coloured speckles; perfumes; foam controllers; and fabric softening compounds. This list is not intended to be exhaustive . Powder flow may be improved by the incorporation of a small amount of an additional powder structurant, for example, a fatty acid (or fatty acid soap) , a sugar, an acrylate or acrylate/maleate polymer, or sodium silicate which is suitably present in an amount of from 1 to 5 wt% . Regarding the equipment used for the mixing stage (s) of the process (i.e. after blending of the ingredients in the 19 liquid component) , the liquid component is preferably admixed with the solid components in a first mixing step in a high-speed mixer/densifier to form a granular detergent material. Optionally, the granular detergent material from the first mixing step may subsequently be treated in a second mixing step in a moderate-speed granulator/densifier . If high bulk density product is desired, at this stage it can be brought into or maintained in the required deformable state. In any event, the product of the first mixing step or the second mixing step may then be cooled and/or dried. The residence time in the high-speed mixer/densifier in the first mixing step is preferably from about 5 to 30 seconds. The residence time in the moderate-speed mixer/densifier during any second (optional) mixing step is preferably from about 1 to 10 minutes. It is preferred to perform any such process as a continuous process but it could be performed as a batch process in a high shear or low shear mode. In the first mixing step, the solid components of the feedstock are very thoroughly mixed with the liquid blend by means of a high-speed mixer/densifier . Such a mixer provides a high energy stirring input and achieves thorough mixing in a very short time . As high-speed mixer/densifier we advantageously used the Lδdige (Trade Mark) CB 30 Recycler. This apparatus essentially consists of a large, static hollow cylinder having a diameter of about 30 cm which is horizontally placed. In the middle, it has a rotating shaft with several different types of blades mounted thereon. It can be rotated at speeds between 100 and 2500 rpm, dependent on the - 20 - degree of densification and the particle size desired. The blades on the shaft provide a thorough mixing action of the solids and the liquids which may be admixed at this stage. The mean residence time is somewhat dependent on the rotational speed of the shaft, the position of the blades and the weir at the exit opening. Other types of high-speed mixers/densifiers having a comparable effect on detergent powders can also be contemplated. For instance, a Shugi (Trade Mark) Granulator or a Drais (Trade Mark) K-TTP 80 may be used. In the first mixing step, the components of the feedstock are thoroughly mixed in a high-speed mixer/densifier for a relatively short time of about 5-30 seconds, preferably under conditions whereby the starting material is brought into, or maintained in, a deformable state, to be defined hereafter . In the case of production of high bulk density products, after the first mixing step, if the resultant detergent material still possesses a considerable porosity, then instead of choosing a longer residence time in the highspeed mixer/densifier to obtain a further bulk density increase, it may then be subjected to the optional second mixing step in which the detergent material is treated for 1-10 minutes, preferably for 2-5 minutes, in a moderate- speed granulator/densifier . During this second processing step, the conditions are such that the powder is brought into, or maintained in, a deformable state. As a consequence, the particle porosity will be further reduced. The main differences with the first step reside in the lower - 21 - mixing speed and the longer residence time of 1-10 minutes, and the necessity for the powder to be deformable. The optional second mixing step can be successfully carried out in a Lodige (Trade Mark) KM 300 mixer, also referred to as Lδdige Ploughshare. This apparatus essentially consists of a hollow static cylinder having a rotating shaft in the middle. On this shaft various plough-shaped blades are mounted. It can be rotated at a speed of 40-160 rpm. Optionally, one or more high-speed cutters can be used to prevent excessive agglomeration. Another suitable machine for this step is, for example the Drais (Trade Mark) K-T 160. However, instead of using a high-speed mixer densifier machine, followed by a separate moderate speed-mixer densifier machine, the same effect could be obtained using a single machine operated at two speeds. It could be operated first at high speed for mixing/densification and then at moderate speed for granulation/densification. Suitable R machines include mixers of the Fukae FS-G series; Diosna V series ex Dierks & Sohne, Germany; Pharma Matrix ex T.K. Fielder Ltd; England; Fuji VG-C series ex Fuji Sangyo Co., Japan; the Roto ex Zanchetta & Co. srl, Italy and the Schugi Flexomix granulator. For use, handling and storage, the densified detergent powder must be in a free flowing state. Therefore, in a final step the powder can be dried and/or cooled if necessary. This step can be carried out in a known manner, 22 for instance in a fluid bed apparatus (drying, cooling) or in an airlift (cooling) . It is advantageous if the powder needs a cooling step only, because the required equipment is relatively simple and more economical. For production of high bulk density products, any optional second mixing step and preferably also for the first mixing step, the detergent powder should be brought into a deformable state in order to get optimal densification. The high-speed mixer/densifier and/or the moderate speed granulator/densifier are then able to effectively deform the particulate material in such a way that the particle porosity is considerably reduced or kept at a low level, and consequently the bulk density is increased. The invention will now be explained in more detail by way of the following non-limiting examples. 23 EXAMPLES : Preparation of detergent powders Powders having the following composition were prepared: Example A (wt%) Example 1 (wt%) Na-LAS 8.68 8.42 Nonionic 7E0 4.55 4.73 Nonionic 3E0 2.44 2.52 Soap 1.12 1.62 Zeolite A24 29.63 25.47 (anhydrous) Na-citrate 3.49 3.51 Light Na-carbonate 5.82 SCMC 40.54 0.53 Moisture, salts, NDOM 4.77 5.21 BASE POWDER 61.05 52.00 POST-DOSED TAED 5.5 5.5 Percarbonate 19.00 19.00 Carbonate (present as 5.83 14.88 Na salt & Nabion 15) Minor ingredients 8.62 8.62 TOTAL 100.00 100.00 The base powders were prepared by formulating the liquid component, admixing the liquid component with the solid components in a continuous Lodige Recycler high speed mixer/granulator for about 10 seconds, transferring the material to a Lodige Ploughshare moderate speed mixer/granulator and mixing for about 3 minutes, and finally drying and cooling the resultant material on a fluid bed to produce a granular base powder. - 24 - Example A Ingredients in liquid component Liquid blend (a) Na-LAS LAS acid Liquid blend (a') Nonionic 7E0 Nonionic 3E0 Fatty acid Example 1 Liquid blend Na-LAS Nonionic 7E0 Nonionic 3E0 Soap Water In the comparative Example A, the liquid components were added as two separate mixtures, liquid blends (a) and (a')/ to the granulator. Blend (a) consisted of a Na-LAS and LAS acid blend, whilst blend (a') consisted of nonionic surfactant and fatty acid. The LAS acid and fatty acid, in blends (a) and (a') respectively, were neutralised to their respective sodium salts by sodium carbonate in the Recycler. In Example 1, the liquid component was added as a single mixture. LAS acid, fatty acid, nonionic surfactant and NaOH were blended in a loop-reactor to produce a liquid blend consisting of Na-LAS, nonionic surfactant, soap and water. The soap in the liquid component acted as a structurant. This blend was then admixed with the solid material in the Lodige Recycler. Residue levels and fabric colour damage in the wash 39 pieces of black fabric made of different fibres and 9 bleach sensitive pieces of fabric were put in a washing machine. 75g of washing powder was dosed via a scuttle and a short wash cycle of 25 minutes carried out at 30°C. After 25 three rinses, the pieces of fabric were dried and assessed visually. The incidences of residues and dye damage were recorded (Table 2). Residue levels were assessed on three scales; patches, particles and films. Dye damage was assessed on a three-point scale of low, medium and high intensity. A score of 5 on the scale of patches means that an average of 5 of the 48 pieces showed patches after the wash. In addition, the total number of pieces that had at least one residue or dye damage spot were counted. Example A Example 1 Incidence of Residues Patch 4.8 0.8 Parts 16.5 6.8 Film 15.8 6.0 Number 23.5 9.5 Incidence of Dye Damage Low 1.2 0.5 Medium 1.2 0.5 High 1.5 none Number 4.0 1.0 It can be clearly seen that by following the process of the invention, as in Example 1, a greater than 50% reduction is achieved in residue levels and dye damage in the wash as compared with the comparative Example A, where no structurant was present in the liquid component.

Claims: - 26 - CLAIMS 1. Use of a process for preparing a granular detergent composition with improved wash-delivery properties, the process comprising the steps of: (i) preparing a liquid component comprising an anionic surfactant or precursor thereof, a nonionic surfactant and a structurant; (ii) admixing the liquid component with a solid component in a high speed mixer/granulator; and optionally (iii) drying and/or cooling, the structurant being incorporated in an amount such that the liquid component is pumpable at temperatures of 50°C or more (e.g. 60°C or more) but causes sufficient solidification during the second and/or third steps to form a free-flowing granulated product. 2. Use of a process for preparing a bleach-containing granular detergent composition which produces less dye damage in the wash, the process comprising the steps of: (i) preparing a liquid component comprising an anionic surfactant or precursor thereof, a nonionic surfactant and a structurant; (ϋ) admixing the liquid component with a solid component in a high speed mixer/granulator; and optionally (iii) drying and/or cooling, the structurant being incorporated in an amount such that the liquid component is pumpable at temperatures of 50°C or more (e.g. 60°C or more) but causes sufficient - 27 - solidification during the second and/or third steps to form a free-flowing granulated product. 3. Use of a process according to claim 1 or 2 , wherein the liquid component is pumpable at a temperature of 60°C or more, preferably 75°C or more. 4. Use of a process according to any one of the preceding claims, wherein the liquid component is solid at below 50°C, preferably at 25°C or less. 5. Use of a process according to any one of the preceding claims, wherein the liquid component solidifies to form a tablet which at 20 a C has a P max value of at least 0.2 M Pa, preferably from 0.3 to 0.5 M Pa and/or an E moc j value of at least 3 M Pa, preferably from 5 to 10 M Pa. 6. Use of a process according to any one of the preceding claims, wherein the anionic surfactant is a alkylbenzene sulphonate. 7. Use of a process according to any one of the preceding claims, wherein the liquid component is substantially non- aqueous . 8. Use of a process according to claim 7, wherein the liquid component contains no more than 15% by weight of water . 9. Use of a process according to any one of the preceding claims, wherein the granular detergent composition can be 28 formed into a tablet having a P max value of at least 0.5 M Pa and/or an E mod value of at least 20 M Pa. 10. Use of a process according to any one of the preceding claims, wherein the solid component comprises a detergency builder material. 11. Use of a process according to claim 10, wherein the detergency builder material comprises an aluminosilicate builder. 12. Use of a process according to any one of the preceding claims, wherein the liquid component contains from 10% to 98% by weight of the liquid component of nonionic surfactant. 13. Use of a process according to any one of the preceding claims, wherein the liquid component contains from 98% to 10% by weight of the liquid component of anionic surfactant. 14. Use of a process according to any one of the preceding claims, wherein the liquid component contains up to 30% by weight of the liquid component of structurant. 15. Use of a process according to any one of the preceding claims, wherein the weight ratio of the liquid component to the solid component is from 0.4:1 to 0.7:1. 16. A process for preparing a granular detergent composition, the process comprising the steps of: 29 - (i) preparing a liquid component comprising surfactant and a structurant, the structurant being incorporated in an amount such that the liquid component is pumpable at temperatures of 50°C or more but causes sufficient solidification during the second and/or third steps to form a free- flowing granulated product; (ii) admixing the liquid component with a solid component in a high speed mixer/granulator; and optionally (iii) drying and/or cooling, wherein the surfactant comprises an anionic surfactant or precursor thereof and a nonionic surfactant, the solid component comprises an aluminosilicate and whereby the granular detergent composition has a disintegration rate of -1 of greater than 25 μms 17. A granular detergent composition with improved dissolution properties obtainable by the process defined in the first aspect, the granular detergent composition comprising an anionic surfactant, a nonionic surfactant, soap and an aluminosilicate builder. 18. A granular detergent composition as claimed in claim 17 in which the anionic surfactant is an alkylbenzene sulphonate .

Inventors: DE KORT BARBARA, EUSER HUUG, MOHLMANN WILLEM MICHAEL M, DE KORT, BARBARA, EUSER, HUUG, MOHLMANN, WILLEM, MICHAEL, M.
Applicants: EUSER HUUG, KORT BARBARA DE, LEVER HINDUSTAN LTD, MOHLMANN WILLEM MICHAEL M, UNILEVER NV, UNILEVER PLC, DE KORT, BARBARA, EUSER, HUUG, HINDUSTAN LEVER LIMITED, MOHLMANN, WILLEM, MICHAEL, M., UNILEVER N.V.
Application year: 1999
Main classification: C11D17
IPC codes: C11D1, C11D3, C11D11